feat(chat): render markdown tables in answers, viewer, and thinking

GFM pipe tables in the shared renderer (TODO.md L6): a table-protection
pass in frontend/assets/markdown.js (fences -> tables -> escape order)
pulls each header+separator+body block out as a placeholder, renders
cells escape-first with the same inline transforms, and reinserts a
semantic <table class="md-table"> inside a horizontal-overflow
.md-table-wrap — so a pipe table in a chat answer, the document
viewer/modal, and the thinking block all render the same semantic
table. Fences win over tables; lone pipes stay text.

- styles.css: .md-table palette rules (PLAN §7.2 tokens, no motion);
  min-width: max-content so a WIDE table keeps its natural width and
  the wrapper is the real scroller (width:100% alone wrapped the wide
  table's cells — proven by the new E2E).
- mock_llm.py: TABLE_TRIGGER ("show me a table") -> byte-stable
  TABLE_ANSWER (3-column table, <img onerror> XSS probe line, wide
  5-column table), checked before DEFLECT_MODE like SUMMARY_MODE.
- tests/fixtures/docs/homelab/tables.md: 3x3 pipe table + pipe-heavy
  fenced block (viewer/fence subject); the shared fixture set grows
  8 -> 9 docs, so every suite pinning the count (added/formats/
  stat-docs/EXPECTED_ROWS) is updated accordingly.
- tests/e2e/test_markdown_tables.py (new, story suite): chat table
  shape + non-deflection, wide-table wrapper scroll (no page
  overflow), XSS probe inert, viewer modal table, fence-not-a-table,
  lone pipe stays text.
- tests/e2e/test_agent_document_tools.py: fix a pre-existing flake —
  the "Calling tool…" label window is ~0.4 s at the mock's 0.1 s
  tool-frame pacing, and a polling expect could stride over it
  (failed 3 of 5 runs on the committed baseline). The pre-submit
  MutationObserver record is the deterministic source of truth; the
  racy to_have_text gate is gone.

uv run pytest: 738 passed, app/ coverage 99% (TOTAL unchanged);
ruff + pyright clean; story E2E 6/6 in isolation; regression E2E
suites (chat_rag, document_viewer, document_summaries, smoke) green.

tests/e2e/test_retrieval_quality.py

@@ -87,9 +87,10 @@ def test_multi_format_import_hidden_doc_excluded(
     """A9 (revised): all seven formats import; hidden (dot) paths never do."""
     summary = _reset_db(mock_llm, seed=True)
     assert summary is not None
-    # Eight A9-format fixture files; .hidden/junk.md must never be walked.
-    assert summary.added == 8
-    assert summary.formats == {"md": 4, "yaml": 1, "json": 1, "py": 1, "txt": 1}
+    # Nine A9-format fixture files (phase 44 added homelab/tables.md);
+    # .hidden/junk.md must never be walked.
+    assert summary.added == 9
+    assert summary.formats == {"md": 5, "yaml": 1, "json": 1, "py": 1, "txt": 1}
 
     # Phase 16: the catalog is admin-only — perform the real form login,
     # then call the API with the signed cookie the browser now holds.
@@ -102,7 +103,7 @@ def test_multi_format_import_hidden_doc_excluded(
     r = httpx.get(f"{app_url}/api/docs", timeout=10, cookies=cookies)
     assert r.status_code == 200
     docs = r.json()["documents"]
-    assert len(docs) == 8
+    assert len(docs) == 9
     assert all(".hidden" not in d["path"] for d in docs)
     assert {d["path"] for d in docs} >= {
         "homelab/container_gitlab/gitlab.md",
@@ -113,7 +114,7 @@ def test_multi_format_import_hidden_doc_excluded(
     }
 
     # The Sources page (we're already on it, signed in) reflects the set.
-    expect(page.locator("#stat-docs")).to_have_text("8")
+    expect(page.locator("#stat-docs")).to_have_text("9")
     expect(page.locator("#docs-tbody tr", has_text=".hidden")).to_have_count(0)