fix(languages): add .mts/.cts extensions and *.spec.tsx test glob to the TypeScript config

[tirth8205]

Problem

• The TypeScript LanguageConfig declares extensions: [".ts", ".tsx"] but omits .mts and .cts, the first-class TypeScript module file extensions (TS 4.7+, used in ESM/nodenext projects — which this repo itself targets, see PR Fix TypeScript runtime .js import resolution #405/fix(extract-import-map): apply NodeNext .js→.ts rewrite (#294) #359). The JavaScript config correctly includes the analogous .mjs and .cjs. Because LanguageRegistry derives its extension map directly from config.extensions, and TreeSitterPlugin (tree-sitter-plugin.ts lines 66-72) builds _extensionToLang the same way, a .mts or .cts file resolves to NULL: it is not detected as TypeScript by getByExtension/getForFile and is skipped entirely by the tree-sitter extraction pipeline. Verified at runtime: getByExtension('.mts') -> NULL, getByExtension('.cts') -> NULL, while getByExtension('.mjs') -> 'javascript' and getByExtension('.cjs') -> 'javascript'. The tree-sitter-typescript grammar parses…
• The TypeScript config's test glob list is tests: ["*.test.ts", "*.spec.ts", "*.test.tsx"]. It covers .test.tsx (the React component test convention) but inconsistently omits *.spec.tsx, even though it covers both .test/.spec for plain .ts. The JavaScript config consistently lists both *.test.js and *.spec.js. The dashboard package is React + TypeScript and uses .tsx files, so Component.spec.tsx test files (a common naming style) are not recognized as tests by the file-pattern classifier, while the equivalent Component.test.tsx is. This causes spec-named TSX test files to be miscategorized as regular source.

Fix

• Change line 6 to include the module extensions, mirroring the JavaScript config: extensions: [".ts", ".tsx", ".mts", ".cts"],
• Add the missing spec-tsx glob for parity with the test-tsx and spec-ts entries: tests: [".test.ts", ".spec.ts", ".test.tsx", ".spec.tsx"],

Testing

Adds unit test(s) that fail before the change and pass after. The full core test suite, eslint, and tsc --noEmit all pass locally on this branch.

Found via a static correctness audit of the TypeScript language config.

🤖 Generated with Claude Code

[thejesh23]

A few concerns before this lands.

1. .d.ts (and .d.mts / .d.cts) still skipped. Declaration files are the most common TS-extension outside .ts/.tsx, and getForFile("foo.d.ts") matches on .ts so they already resolve — but the extractor then sees a pure-types file (no runtime exports, no call edges). Worth either explicitly listing .d.ts / .d.mts / .d.cts and gating them out of call-graph extraction, or adding a short comment in the config explaining that .d.ts is intentionally not separated. Otherwise the next person doing this audit lands a third PR.

2. .mts / .cts now route to the plain TS grammar — confirm that's intended. tree-sitter-plugin.ts lines 111-118 hard-code ext === ".tsx" ? "tsx" and falls through to _extensionToLang.get(ext) for everything else. So .mts and .cts will use tree-sitter-typescript.wasm, which is correct (they don't carry JSX). Worth a one-line code comment on that special-case so a future reader doesn't add .mts to the TSX branch by analogy with the .mjs-treated-as-JS pattern.

3. Test glob shape only covers root-level patterns. *.test.tsx / *.spec.tsx are bare globs (no **/ prefix and no __tests__/*.tsx). Vitest's default include is **/*.{test,spec}.?(c|m)[jt]s?(x) and most repos colocate under src/**/__tests__/. Depending on how filePatterns.tests is consumed (couldn't find a hot caller in src/ besides the new test) this may already not match packages/foo/src/__tests__/bar.test.tsx. Worth confirming the matcher is suffix-based, or extending to **/__tests__/*.{ts,tsx} for parity with how the layer-detector already treats __tests__ as a test dir (analyzer/layer-detector.ts:58).

Nit: while you're here, JS config's tests is missing *.test.jsx / *.spec.jsx — same asymmetry you just fixed on the TS side, one config over.

[tirth8205]

1. .d.ts / .d.mts / .d.cts — Added a comment in typescript.ts documenting that declaration files intentionally fall through to .ts / .mts / .cts and are parsed as ordinary types-only TypeScript (no separate call-graph gating). I did not add extractor gating: this behavior predates this PR (.d.ts already resolved via .ts before .mts/.cts were added), so special-casing the extractor is a behavior change outside the module-variant-extension scope here and risks regressing types-only parsing. Tracking the gating idea as a follow-up.

2. .mts / .cts route to plain TS grammar — Confirmed correct: languageKeyFromPath only special-cases ext === ".tsx" → synthetic tsx key; everything else (including .mts/.cts) falls through to _extensionToLang.get(ext) → typescript → tree-sitter-typescript.wasm. Added the requested one-line comment so a future reader doesn't add .mts to the .tsx branch by analogy with the .mjs-as-JS pattern.

3. Test glob shape — Not extending the globs. LanguageConfig.filePatterns.tests has no runtime matcher consumer anywhere in src/ (verified by content grep — only config definitions and the registry test read it; it's z.array(z.string()) declarative metadata). The filePatterns in layer-detector.ts/llm-analyzer.ts is an unrelated LLM-supplied layer-prefix field, and __tests__ layer detection is handled independently by the hardcoded LAYER_PATTERNS in layer-detector.ts. Adding **/__tests__/*.{ts,tsx} would introduce unused, potentially misleading config rather than change any matching behavior.

Nit (JS .jsx test patterns) — Fixed for parity: added *.test.jsx / *.spec.jsx to javascriptConfig.filePatterns.tests, with a test locking it. (No functional effect today given #3, but it removes the cross-config asymmetry.)

Full core suite green (694 passed); tsc --noEmit clean.