test: cover help_md keys, header smoke, and bilingual ES smoke

Two stale Spanish smoke assertions still expected English page titles
for PDF Extractor and Reconciler — the i18n work landed real
translations ("PDF a CSV", "Reconciliar dos archivos"), so refresh the
expected substrings and the surrounding comment.

Add new coverage for the help-popover feature:
- TestHelpPopoverKeys (test_lang_packs): every tool_id resolves a
  non-empty tools.<id>.help_md in BOTH packs; help.button_label and
  help.missing_body resolve in both.
- TestDescriptionCopy (test_tools_registry): every Tool.description
  non-empty and under 120 chars — pins the post-jargon-scrub copy
  so future drift back into multi-clause prose is loud.
- TestRenderToolHeaderSmoke: render_tool_header is callable, listed
  in components.__all__, and every i18n key it touches resolves in
  both packs. Runs without a Streamlit script context.

Suite: 2427 passed (+9 new), 91 skipped.

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

tests/test_tools_registry.py

@@ -157,6 +157,78 @@ class TestLocalizedAccessors:
         assert label and label != f"nav.section_{section}"
 
 
+class TestDescriptionCopy:
+    """The post-jargon-strip descriptions are intentionally tight one-
+    liners. Pin them so future drift toward bloated marketing copy
+    (or an accidentally-empty string) is caught by CI."""
+
+    # Roomy upper bound; the tightest description today is ~60 chars
+    # and the longest is just over 90. ~120 leaves headroom for minor
+    # copy tweaks without inviting paragraph-length card bodies.
+    _MAX_DESCRIPTION_CHARS = 120
+
+    def test_every_description_is_non_empty(self):
+        empty = [t.tool_id for t in TOOLS if not t.description.strip()]
+        assert not empty, f"tools with empty descriptions: {empty}"
+
+    def test_every_description_under_max_chars(self):
+        too_long = [
+            (t.tool_id, len(t.description))
+            for t in TOOLS
+            if len(t.description) > self._MAX_DESCRIPTION_CHARS
+        ]
+        assert not too_long, (
+            f"tool descriptions exceed {self._MAX_DESCRIPTION_CHARS} chars: "
+            f"{too_long}"
+        )
+
+
+class TestRenderToolHeaderSmoke:
+    """``render_tool_header`` is the helper every tool page now calls in
+    place of ``st.title(...) + st.caption(...)``. We can't render it
+    without a Streamlit script context, but we CAN verify it imports
+    cleanly via the public ``src.gui.components`` surface and resolves
+    the expected i18n keys for a known tool id."""
+
+    def test_importable_from_public_components_package(self):
+        from src.gui.components import render_tool_header
+
+        assert callable(render_tool_header)
+
+    def test_listed_in_public_all(self):
+        # The public ``__all__`` is what per-tool builds key off; a
+        # removal here would silently break tool pages that import
+        # from ``src.gui.components`` directly.
+        from src.gui import components as components_pkg
+
+        assert "render_tool_header" in components_pkg.__all__
+
+    def test_resolves_expected_i18n_keys_for_known_tool(self):
+        # The helper reads four pack keys per render:
+        # ``tools.<id>.page_title``, ``tools.<id>.page_caption``,
+        # ``tools.<id>.help_md``, plus shared ``help.button_label`` /
+        # ``help.missing_body``. We don't invoke the helper (no script
+        # context) — we verify the keys it would touch resolve to
+        # non-empty strings in both packs.
+        from src.i18n import t as _t
+
+        tool_id = "02_text_cleaner"
+        for lang in ("en", "es"):
+            for suffix in ("page_title", "page_caption", "help_md"):
+                key = f"tools.{tool_id}.{suffix}"
+                value = _t(key, lang)
+                assert value and value != key, (
+                    f"render_tool_header({tool_id!r}) "
+                    f"would render the literal key {key!r} in {lang!r}"
+                )
+            for key in ("help.button_label", "help.missing_body"):
+                value = _t(key, lang)
+                assert value and value != key, (
+                    f"render_tool_header would render the literal key "
+                    f"{key!r} in {lang!r}"
+                )
+
+
 class TestReconcilerAndPdfArePresent:
     """The two newest pages were the most likely to be forgotten in
     the registry — pin them explicitly so a regression flagging