Fix Typst: support multi-line math blocks ($ ... multi-line ... $)

mathContentTokenizer was stopping at newlines, causing a parse error for
Typst block math that spans multiple lines.  The parser then entered a bad
state that cascaded: the stale error-recovery left the item* parser in a
degraded mode, causing body text below the math block to be highlighted as
t.string (orange).

Fix: switch to contextual: true (only fires inside InlineMath where
MathContent is actually expected) and remove the newline restriction so
the tokenizer reads until the closing '$' regardless of line boundaries.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/web/frontend/js/features/source-editor/lezer-typst/tokens.mjs

@@ -238,19 +238,26 @@ export const lineCommentContentTokenizer = new ExternalTokenizer(
 )
 
 // ── mathContentTokenizer ────────────────────────────────────────────────
-// Emits MathContent — everything between the $...$ delimiters (no newlines).
-// External rather than a @tokens rule for the same reason as LineCommentContent:
-// ![$\n]+ overlaps with spaces, '<', '@', and other literals in merged states.
+// Emits MathContent — everything between the $...$ delimiters.
+//
+// contextual: true — only fires when MathContent is in the valid set, i.e.
+// inside InlineMath → "$" . MathContent? "$".  This prevents the tokenizer
+// from consuming body text in LALR-merged states.
+//
+// No newline restriction: Typst block math spans multiple lines
+// ($ formula \n continuation $), so we must read until the closing '$'
+// regardless of newlines.  The grammar's InlineMath rule handles both inline
+// ($x^2$) and block ($ ... $) forms with the same production.
 export const mathContentTokenizer = new ExternalTokenizer(
   (input, _stack) => {
     let hasContent = false
-    while (input.next !== -1 && input.next !== DOLLAR && input.next !== NEWLINE) {
+    while (input.next !== -1 && input.next !== DOLLAR) {
       input.advance()
       hasContent = true
     }
     if (hasContent) input.acceptToken(MathContent)
   },
-  { contextual: false }
+  { contextual: true }
 )
 
 // ── codeKeywordTokenizer ─────────────────────────────────────────────────