feat(audit): /logs page — view + download recent audit log files

Adds a Streamlit page at ``/logs`` listing every
``datatools-*.jsonl`` file in ``audit_log_dir()`` (7-day window
per the retention sweep in b3ae913). Each entry shows filename,
mtime, byte size, and a ``st.download_button``. Today's file
gets its own section at the top.

The page also surfaces both paths as copyable monospace text:
the active log path (so users can grep/cat it directly on their
machine) and the folder path (so they can paste into Explorer /
Finder).

Wired into navigation via ``st.Page("pages/_Logs.py", ...)`` with
``url_path="logs"``. The sidebar entry is hidden by the same
``hide_streamlit_chrome`` CSS rule that hides ``/activate`` and
``/close`` — same pattern, same ``:has()`` + plain-fallback
selectors so the LinkContainer collapses cleanly in modern
browsers and the anchor is at least un-clickable in older ones.

License gate is OFF for this page (``gate_license=False``) — if a
user's license expires they may need logs to file a support
request; locking them out of their own audit history would be
hostile.

Next commit will wire the popover link.

Rollback: ``git revert HEAD`` removes the page and its nav entry;
the audit log itself keeps working.

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

src/gui/app.py

@@ -116,6 +116,12 @@ def _build_navigation() -> dict[str, list]:
         icon=":material/key:",
         url_path="activate",
     )
+    logs = st.Page(
+        "pages/_Logs.py",
+        title="Logs",
+        icon=":material/description:",
+        url_path="logs",
+    )
     close = st.Page(
         "pages/99_Close.py",
         title=_t("nav.close_title") or "Close",
@@ -129,7 +135,7 @@ def _build_navigation() -> dict[str, list]:
     # ``href``, leaving Home visible and no orphan section header /
     # drilldown marker in the sidebar.
     return {
-        "": [home, activate, close],
+        "": [home, activate, logs, close],
         section_label("cleaners"): by_section["cleaners"],
         section_label("transformations"): by_section["transformations"],
         section_label("automations"): by_section["automations"],

src/gui/components/_legacy.py

@@ -79,6 +79,8 @@ footer {
    container's spacing would still occupy a row. */
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/activate"]),
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/activate/"]),
+[data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/logs"]),
+[data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/logs/"]),
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/close"]),
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/close/"]) {
     display: none !important;
@@ -87,6 +89,8 @@ footer {
    least hide the anchor itself so the entry isn't clickable. */
 [data-testid="stSidebarNav"] a[href$="/activate"],
 [data-testid="stSidebarNav"] a[href$="/activate/"],
+[data-testid="stSidebarNav"] a[href$="/logs"],
+[data-testid="stSidebarNav"] a[href$="/logs/"],
 [data-testid="stSidebarNav"] a[href$="/close"],
 [data-testid="stSidebarNav"] a[href$="/close/"] {
     display: none !important;

src/gui/pages/_Logs.py

@@ -0,0 +1,109 @@
+"""Logs — view and download recent audit log files.
+
+Reached from the sticky-footer Help popover (no sidebar entry — the
+nav link is hidden via CSS in ``hide_streamlit_chrome``). URL path
+is ``/logs``. Lists every ``datatools-*.jsonl`` file in
+``audit_log_dir()`` so users can download today's session or a
+prior day's file for support requests.
+
+The 7-day retention sweep in ``src/audit.py`` runs on the writer
+thread, so this page is read-only — no delete buttons. Users
+wanting a longer retention can copy files out of the folder.
+"""
+
+from __future__ import annotations
+
+import sys
+from datetime import datetime
+from pathlib import Path
+
+import streamlit as st
+
+_project_root = Path(__file__).resolve().parent.parent.parent.parent
+if str(_project_root) not in sys.path:
+    sys.path.insert(0, str(_project_root))
+
+from src.audit import _RETENTION_DAYS, audit_log_dir, audit_log_path
+from src.gui.components import hide_streamlit_chrome, render_sticky_footer
+
+_ICON_PATH = str(Path(__file__).parent.parent / "assets" / "datatools_icon_256.png")
+st.set_page_config(
+    page_title="Logs · DataTools",
+    page_icon=_ICON_PATH,
+    layout="wide",
+)
+
+hide_streamlit_chrome(gate_license=False)
+render_sticky_footer()
+
+
+st.markdown("# Logs")
+st.caption(
+    f"Activity logs are written to disk one file per day and kept "
+    f"for {_RETENTION_DAYS} days. Event timestamps inside each file "
+    f"are UTC; filenames use your local date."
+)
+
+log_dir = audit_log_dir()
+today_path = audit_log_path()
+
+st.markdown("### Today")
+st.code(str(today_path), language="text")
+if today_path.exists():
+    size = today_path.stat().st_size
+    st.caption(f"{size:,} bytes")
+    try:
+        data = today_path.read_bytes()
+        st.download_button(
+            label=f"Download {today_path.name}",
+            data=data,
+            file_name=today_path.name,
+            mime="application/x-ndjson",
+            key="dl_today",
+        )
+    except Exception as e:
+        st.warning(f"Could not read today's log: {type(e).__name__}: {e}")
+else:
+    st.caption("No events written yet this session.")
+
+st.markdown("### Older sessions")
+if not log_dir.exists():
+    st.caption("No logs folder yet.")
+else:
+    others = sorted(
+        (p for p in log_dir.glob("datatools-*.jsonl") if p != today_path),
+        key=lambda p: p.stat().st_mtime,
+        reverse=True,
+    )
+    if not others:
+        st.caption("No older log files.")
+    else:
+        for p in others:
+            try:
+                st_mtime = datetime.fromtimestamp(p.stat().st_mtime)
+                size = p.stat().st_size
+                cols = st.columns([4, 2, 2])
+                cols[0].markdown(f"`{p.name}`")
+                cols[1].caption(
+                    f"{st_mtime:%Y-%m-%d %H:%M} · {size:,} bytes"
+                )
+                with cols[2]:
+                    st.download_button(
+                        label="Download",
+                        data=p.read_bytes(),
+                        file_name=p.name,
+                        mime="application/x-ndjson",
+                        key=f"dl_{p.name}",
+                    )
+            except Exception as e:
+                st.caption(
+                    f"`{p.name}` — could not read: "
+                    f"{type(e).__name__}: {e}"
+                )
+
+st.markdown("### Folder")
+st.code(str(log_dir), language="text")
+st.caption(
+    "Copy this path into Explorer / Finder / your file manager to "
+    "open the folder directly."
+)