fix(wiki): protect math in cross-refs; drop no-op DB call; fix mark order

- R-9 (MED): _inject_cross_refs now protects LaTeX math spans ($…$, $$…$$,
  \(…\), \[…\]) like inline code, so a concept name inside a formula is no longer
  rewritten to a [[slug]] link and corrupting the LaTeX. Regression test added.
- C-13 (LOW): mark ungrounded claims on the raw body BEFORE injecting cross-refs
  (render then inject), so a concept name inside a claim cannot stop the ⚠ regex
  from matching.
- C-12 (LOW): _try_embed_formulas is now a true no-op — it previously issued a
  per-concept information_schema round-trip that did nothing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/wiki/test_compile.py

@@ -274,6 +274,19 @@ def test_inject_cross_refs_skips_inline_code() -> None:
     assert "[[circle-packing]]" in result  # bare occurrence replaced
 
 
+def test_inject_cross_refs_skips_math_spans() -> None:
+    """Concept names inside LaTeX math are NOT rewritten to [[slug]] links (audit R-9)."""
+    concepts = [
+        Concept(slug="energy", title="Energy", aliases=[]),
+        FIXTURE_CONCEPT,
+    ]
+    text = "Prose Energy here. Math $x = Energy^2$ and inline \\(Energy\\) stay literal."
+    result = _inject_cross_refs(text, concepts, current_slug="lobachevsky-function")
+    assert "$x = Energy^2$" in result  # display/inline $...$ math untouched
+    assert "\\(Energy\\)" in result  # \(...\) math untouched
+    assert "Prose [[energy]] here." in result  # prose occurrence still linked
+
+
 def test_inject_cross_refs_full_list_even_when_single_concept() -> None:
     """Cross-ref injection uses the full concept list, not just the compiled concept."""
     concepts = [