feat(ui): page header + files card + action bar + findings cards (mockup 2)

Closes the remaining gaps between the live home page and the
``datatools_layout_redesign2.html`` mockup. Four pieces land
together because they all consume the same new CSS scaffold:

1. Page header (§page-header)
   ``st.title`` + ``st.caption`` + ``st.divider`` collapse into one
   flex header: h1 + body subtitle on the left, ``Runs 100% locally``
   privacy pill (success-fill + lock SVG) on the right, soft border
   below. The "Runs 100% locally" phrase moved out of
   ``home.caption`` into the new ``home.privacy_pill`` i18n key
   (en + es).

2. Files card (§files-card)
   The "Imported files" list is now a single bordered card with a
   section head (count + KB total on the right, mockup §section-head).
   Each row renders a 28px accent-fill chip carrying the inline
   document SVG, a mono filename, a right-aligned mono size, and a
   compact ``✕`` button. The word-button ``Remove`` is gone —
   replaced by an icon-only tertiary button styled via a new CSS
   rule that goes transparent → danger-fill on hover (mockup
   §file-remove).

3. Action bar (§action-bar)
   Three buttons in one row: ``Run analysis`` (primary ink), a new
   disabled ``Export report`` (secondary; coming soon, tooltip), and
   ``Clear results``. New i18n key ``upload.export_report``.

4. Findings — per-file group cards (§finding-group)
   ``render_findings_panel`` rewritten end-to-end. Output is now:
     • A head row (``dt-finding-group-head``) bleeding to the card
       edges: worst-severity dot · mono filename · count pills
       enumerating non-zero severities (e.g. ``2 info`` blue,
       ``1 warning`` amber, ``1 error`` rose).
     • A flat list of finding rows sorted error → warn → info.
       Each row: tinted Material-icon chip + title (description
       with optional ``<code>`` column chip) + mono meta line
       (rows affected, samples captured) + tertiary
       ``Open <Tool> →`` action button that ``st.switch_page``s
       to the relevant tool.
   The previous tool-grouped expander stack is dropped — the new
   layout is denser and matches the mockup's single-card-per-file
   structure.

   ``_render_one_finding`` (the old per-finding helper that emitted
   markdown lines + sample tables) remains in the file but is no
   longer called from the home flow; left in place for any other
   surface that still depends on the markdown style.

   The "no issues" success state renders a green dot + mono
   filename + ``no issues`` success pill in the same card chrome,
   so empty-result files visually match the rest of the panel
   rather than getting a generic ``st.success`` callout.

CSS additions (``_DESIGN_TOKENS_CSS``):
  ``.dt-page-header / .dt-page-subtitle / .dt-privacy-pill``
  ``.dt-files-section-head / .dt-section-meta``
  ``.dt-file-row / .dt-file-icon-chip / .dt-file-name / .dt-file-size``
  ``.dt-finding-group-head / .dt-severity-dot{.warn,.info,.error,.success}``
  ``.dt-group-filename / .dt-group-counts``
  ``.dt-count-pill{.warn,.info,.error,.success}``
  ``.dt-finding-row / .dt-finding-icon{.warn,.info,.error}``
  ``.dt-finding-title / .dt-finding-meta``
  Tertiary button rule (transparent → danger-fill on hover) for
  the X button and the ``Open Tool →`` row action.

theme.py:
  Explicitly loads Material Symbols Outlined alongside Geist —
  the severity-chip ligatures (``info`` / ``warning`` / ``error``)
  need the font present even when no ``:material/`` token has been
  emitted yet on the page. Tightened ``.dt-finding-icon .dt-mui``
  selector with ``[data-testid="stMarkdownContainer"]``-scoped
  variant so the Material font wins over theme.py's base
  ``var(--font-sans) !important`` on markdown descendants.

Leading section-heading emojis stripped from i18n
(``upload.heading``) for parity with the mockup's clean ``Files``
/ ``Findings`` h2s.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/gui/_home.py

@@ -161,9 +161,30 @@ def _home_page() -> None:
     hide_streamlit_chrome()
     render_sticky_footer()
 
-    st.title(t("home.title"))
-    st.caption(t("home.caption"))
-    st.divider()
+    import html as _html
+    # Page header — h1 + body subtitle on the left, privacy pill on
+    # the right (mockup §page-header). Rendered as a single HTML block
+    # so the title/subtitle/pill share one flex row; ``st.title`` +
+    # ``st.caption`` + ``st.divider`` would stack vertically and lose
+    # the right-aligned pill. Bottom border replaces the explicit
+    # ``st.divider`` that used to sit below the caption.
+    privacy_label = _html.escape(t("home.privacy_pill"))
+    st.markdown(
+        '<header class="dt-page-header">'
+        '<div>'
+        f'<h1>{_html.escape(t("home.title"))}</h1>'
+        f'<p class="dt-page-subtitle">{_html.escape(t("home.caption"))}</p>'
+        '</div>'
+        '<span class="dt-privacy-pill">'
+        '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor">'
+        '<rect x="4" y="11" width="16" height="10" rx="2"/>'
+        '<path d="M8 11V7a4 4 0 018 0v4"/>'
+        '</svg>'
+        f'{privacy_label}'
+        '</span>'
+        '</header>',
+        unsafe_allow_html=True,
+    )
 
     st.markdown(f"### {t('upload.heading')}")
     st.caption(t("upload.intro_multi"))
@@ -211,27 +232,59 @@ def _home_page() -> None:
     #    interleaving widget-key updates with state changes.
     if home_uploads:
         import hashlib
-        st.markdown("**Imported files**")
+        # Files-card head: count + total size (mockup §section-head).
+        total_bytes = sum(meta["size"] for meta in home_uploads.values())
+        if total_bytes >= 1024:
+            total_label = f"{total_bytes / 1024:.1f} KB"
+        else:
+            total_label = f"{total_bytes:,} B"
+        n_files = len(home_uploads)
+        files_word = "file" if n_files == 1 else "files"
+        st.markdown(
+            '<div class="dt-files-section-head">'
+            f'<h3>Imported files</h3>'
+            f'<span class="dt-section-meta">{n_files} {files_word}'
+            f' · {_html.escape(total_label)} total</span>'
+            '</div>',
+            unsafe_allow_html=True,
+        )
+
         to_remove: str | None = None
-        for name in list(home_uploads.keys()):
-            digest = hashlib.sha1(
-                name.encode("utf-8"), usedforsecurity=False,
-            ).hexdigest()[:10]
-            col_file, col_remove = st.columns([8, 1])
-            col_file.markdown(
-                f"📄 `{name}` &nbsp; "
-                f"<span style='opacity:0.6'>"
-                f"({home_uploads[name]['size']:,} bytes)</span>",
-                unsafe_allow_html=True,
-            )
-            if col_remove.button(
-                "Remove",
-                key=f"_home_remove_{digest}",
-                help=f"Remove {name}",
-                type="secondary",
-                width="stretch",
-            ):
-                to_remove = name
+        # Document-icon SVG used by every file row's icon chip
+        # (mockup §file-row .file-icon).
+        _DOC_SVG = (
+            '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor">'
+            '<path d="M14 2H6a2 2 0 00-2 2v16a2 2 0 002 2h12a2 2 0 002-2V8z"/>'
+            '<path d="M14 2v6h6"/>'
+            '</svg>'
+        )
+        with st.container(border=True):
+            for name in list(home_uploads.keys()):
+                digest = hashlib.sha1(
+                    name.encode("utf-8"), usedforsecurity=False,
+                ).hexdigest()[:10]
+                col_name, col_size, col_x = st.columns([8, 1.6, 0.55])
+                col_name.markdown(
+                    '<div class="dt-file-row">'
+                    f'<span class="dt-file-icon-chip">{_DOC_SVG}</span>'
+                    f'<span class="dt-file-name">{_html.escape(name)}</span>'
+                    '</div>',
+                    unsafe_allow_html=True,
+                )
+                col_size.markdown(
+                    f'<div style="text-align:right;">'
+                    f'<span class="dt-file-size">'
+                    f'{home_uploads[name]["size"]:,} B'
+                    '</span></div>',
+                    unsafe_allow_html=True,
+                )
+                if col_x.button(
+                    "✕",
+                    key=f"_home_remove_{digest}",
+                    help=f"Remove {name}",
+                    type="tertiary",
+                ):
+                    to_remove = name
 
         if to_remove is not None:
             from src.audit import log_event
@@ -288,7 +341,9 @@ def _home_page() -> None:
 
     pending = [name for name in home_uploads if name not in findings_by_file]
 
-    col_run, col_clear, _ = st.columns([1, 1, 4])
+    # Action bar — Run / Export report (disabled, coming soon) /
+    # Clear results, matching the mockup §action-bar.
+    col_run, col_export, col_clear, _ = st.columns([1, 1, 1, 3])
     with col_run:
         run_clicked = st.button(
             t("upload.run_button"),
@@ -297,6 +352,14 @@ def _home_page() -> None:
             disabled=not pending,
             width="stretch",
         )
+    with col_export:
+        st.button(
+            t("upload.export_report"),
+            key="home_export_report",
+            disabled=True,
+            help="Coming soon",
+            width="stretch",
+        )
     with col_clear:
         clear_clicked = st.button(
             t("upload.clear_results"),
@@ -340,11 +403,19 @@ def _home_page() -> None:
             findings = findings_by_file[name]
             with st.container(border=True):
                 if not findings:
-                    st.markdown(f"### 📄 {name}")
-                    st.success(t("findings.none"))
+                    st.markdown(
+                        '<div class="dt-finding-group-head">'
+                        '<span class="dt-severity-dot success"></span>'
+                        f'<span class="dt-group-filename">{_html.escape(name)}</span>'
+                        '<div class="dt-group-counts">'
+                        '<span class="dt-count-pill success">no issues</span>'
+                        '</div>'
+                        '</div>',
+                        unsafe_allow_html=True,
+                    )
                 else:
                     render_findings_panel(
                         findings,
-                        header=f"📄 {name}",
+                        header=name,
                         key_namespace=name,
                     )