[codex] fix string highlighting after static assert

[csyonghe]

Summary

Fixes a Slang TextMate grammar leak where a quoted diagnostic string containing a qualified call-like token, such as _Texture::SampleCmpLevel(...), could cause subsequent code to remain highlighted as part of the string/meta scope.

Root Cause

The meta.qualified.type.call.slang lookahead could scan through quoted text after Shape.dimensions, find _Texture::SampleCmpLevel( inside the string literal, and incorrectly keep the qualified-call scope active. The string rules also had no end-of-line fallback, which made leaks more visible when a string scope failed to close cleanly.

Changes

• Stop the qualified type-call lookahead at quote characters.
• Let single and double quoted strings terminate at the closing quote or end of line.

Validation

• Parsed syntaxes/slang.tmLanguage.json with ConvertFrom-Json.
• Ran a VS Code TextMate tokenizer smoke test confirming the static_assert string closes, the following if is scoped as keyword.control.slang, escaped quotes still work, and unterminated strings do not leak into the next line.