Escape LaTeX-special characters in plot titles/xlabels (gitea #81)

shower_containment_depth_90/95's title contains a literal "%" (e.g.
"...(90% of deposited energy)"), which usetex reads as a comment marker
and aborts LaTeX compilation. Since render_all processes reduced JSON
files in sorted filename order, this killed every plot id sorting after
these two in the same run.

Escape title/xlabel once, centrally, in render()'s dispatch (the one
place every renderer kind draws them from before handing off to
plotstyle/matplotlib) rather than at each catalog.py call site, so any
future catalog title with a %, &, #, etc. is covered automatically.
_plot_metadata keeps using the unescaped Reduced for the gallery YAML,
since that's not LaTeX.

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

tests/test_render.py

@@ -461,3 +461,30 @@ def test_plot_metadata_omits_parameters_when_run_meta_empty():
     meta = render_mod._plot_metadata(r, {})
     assert "parameters" not in meta
     assert "note" not in meta
+
+
+def test_tex_escape_handles_percent_and_other_special_chars():
+    assert render_mod._tex_escape("90% of deposited energy") == r"90\% of deposited energy"
+    assert render_mod._tex_escape(r"a_b & c#d $e {f} \bar") == r"a\_b \& c\#d \$e \{f\} \textbackslash{}bar"
+
+
+def test_render_survives_title_and_xlabel_with_literal_percent(tmp_path: Path):
+    # Regression test for gitea #81: a literal "%" in a catalog title (e.g.
+    # "Shower containment depth (90% of deposited energy)") crashed the whole
+    # LaTeX render, since usetex treats an unescaped "%" as a comment marker.
+    reduced = [
+        Reduced(
+            "shower_containment_depth_90",
+            "shower",
+            "single_hist",
+            "Shower containment depth (90% of deposited energy)",
+            "depth containing 90% of deposited energy [mm]",
+            {"edges": [0, 1, 2], "series": {"flow": [5, 1]}},
+        ),
+    ]
+    try:
+        pdfs = _try_render(reduced, tmp_path)
+    except RuntimeError as e:  # LaTeX missing at render time
+        pytest.skip(f"LaTeX rendering unavailable: {e}")
+    assert len(pdfs) == 1
+    assert pdfs[0].exists()