fix(stage-371): apply Opus SHOULD-FIX — KaTeX/CSV/diff stay LTR + chip 1px boundary

Opus advisor on stage-371 caught three issues during pre-release review:

1. RTL salvage missed KaTeX math (display equations + inline LaTeX), diff
   blocks, CSV tables (column order must read left-to-right regardless of
   chat direction), and .skill-file-path. The first salvage commit only
   covered pre/code/kbd/samp/tt and tool-call bodies. Added a second
   force-LTR block covering: .katex, .katex-block, .katex-display,
   .katex-html, .katex-inline, .diff-block (+children), .csv-table-wrap,
   .csv-table (+children), .skill-file-path. Severity: KaTeX is the most
   user-visible gap — any user rendering math under RTL would see flipped
   equations.

2. Quota chip @media (max-width:1400px) hide rule conflicted at exactly
   1400px with the existing @media (min-width:1400px) .messages-inner
   rule — chip was hidden AT the wide-desktop boundary where it should
   first appear. Changed to (max-width:1399.98px). Visually verified at
   1400px: chip now correctly visible there.

3. Dead .icon-btn.provider-quota-chip selector — chip never has icon-btn
   class. Removed.

Test added: test_rtl_math_and_tables_stay_ltr (pins the 4 new LTR
surfaces). Also removed dead code in test_rtl_code_blocks_stay_ltr
(unused code_block variable).

Per stage-fix protocol: SHIP-with-followup applied on the stage rather
than the source PR, since #2409 is already merged-into-stage and
nesquena-approved. Stage-371 review-bypass batch path still holds.

static/style.css

@@ -1154,9 +1154,13 @@
      mobile-config drawer; laptop desktop users can find quota in
      Settings → Providers (the chip's onclick target). Show only on wide
      desktop where there's genuine room. Aron's standing position on
-     composer real estate (PR #1721, May 13 2026) reinforces this. */
-  @media (max-width:1400px){
-    .icon-btn.provider-quota-chip,
+     composer real estate (PR #1721, May 13 2026) reinforces this.
+
+     Using 1399.98px rather than 1400px to avoid the one-pixel boundary
+     overlap with the existing @media (min-width:1400px) `.messages-inner`
+     rule at line 893 — at exactly 1400px both would fire, so the chip
+     was hidden AT the wide-desktop boundary where it should first appear. */
+  @media (max-width:1399.98px){
     .provider-quota-chip{display:none!important;}
   }
   /* Increased specificity (.icon-btn.composer-mobile-config-btn) to win the cascade
@@ -4086,6 +4090,25 @@ main.main.showing-logs > #mainLogs{display:flex;}
   text-align:left;
   unicode-bidi:isolate;
 }
+/* Force LTR for content classes that render English-by-design even in chat:
+   KaTeX equations (math is LTR-only in standard notation), diff hunks
+   (file paths + line numbers), CSV tables (column order must stay
+   left-to-right), and skill file paths. */
+.chat-content-rtl .msg-body .katex,
+.chat-content-rtl .msg-body .katex-block,
+.chat-content-rtl .msg-body .katex-display,
+.chat-content-rtl .msg-body .katex-html,
+.chat-content-rtl .msg-body .katex-inline,
+.chat-content-rtl .msg-body .diff-block,
+.chat-content-rtl .msg-body .diff-block *,
+.chat-content-rtl .msg-body .csv-table-wrap,
+.chat-content-rtl .msg-body .csv-table,
+.chat-content-rtl .msg-body .csv-table *,
+.chat-content-rtl .msg-body .skill-file-path{
+  direction:ltr;
+  text-align:left;
+  unicode-bidi:isolate;
+}
 /* Tool-call content (commands, paths, JSON) stays LTR. */
 .chat-content-rtl .tool-call-group-body,
 .chat-content-rtl .tool-call-group-body *,

tests/test_pr1721_rtl_salvage.py

@@ -61,9 +61,6 @@ def test_rtl_code_blocks_stay_ltr():
     assert ".chat-content-rtl .msg-body pre" in css
     assert ".chat-content-rtl .msg-body code" in css
     # Must force direction:ltr inside code containers
-    code_block = css.split(".chat-content-rtl .msg-body pre")[1].split("}")[0]
-    # The chain ends in a single declaration block — find the closest declaration
-    # to confirm direction:ltr is present in the code-scoped rule
     code_section_start = css.index(".chat-content-rtl .msg-body pre,")
     code_section_end = css.index("}", code_section_start)
     code_section = css[code_section_start:code_section_end]
@@ -76,6 +73,24 @@ def test_rtl_code_blocks_stay_ltr():
     assert "direction:ltr" in tool_section
 
 
+def test_rtl_math_and_tables_stay_ltr():
+    """KaTeX math, diff blocks, CSV tables, and file paths stay LTR even under RTL.
+    Opus advisor catch on stage-371 (2026-05-16): math is LTR-only in standard
+    notation, CSV columns must read left-to-right regardless of locale."""
+    css = STYLE.read_text(encoding="utf-8")
+    katex_section_start = css.index(".chat-content-rtl .msg-body .katex,")
+    katex_section_end = css.index("}", katex_section_start)
+    katex_section = css[katex_section_start:katex_section_end]
+    # Must include all four key surfaces
+    assert ".katex-display" in katex_section
+    assert ".diff-block" in katex_section
+    assert ".csv-table" in katex_section
+    assert ".skill-file-path" in katex_section
+    # Must force direction:ltr
+    assert "direction:ltr" in katex_section
+    assert "text-align:left" in katex_section
+
+
 def test_rtl_setting_round_trips_through_panels_js():
     js = PANELS.read_text(encoding="utf-8")
     # Load path: read from settings + localStorage, apply class