chore: remove 62 tsc emit artifacts from src/, add noEmit to tsconfig

tsc was emitting compiled .js files directly into packages/web/src/
alongside the .tsx source files because noEmit was not set. These
artifacts were never used — Vite compiles from .tsx source directly.

- Add noEmit: true to packages/web/tsconfig.json (tsc = type-check only)
- Delete all 62 orphaned .js files from src/ (-6,129 lines)
- Add packages/web/src/**/*.js to .gitignore as safeguard

packages/web/tsconfig.json

@@ -11,6 +11,7 @@
     "forceConsistentCasingInFileNames": true,
     "resolveJsonModule": true,
     "isolatedModules": true,
+    "noEmit": true,
     "noUncheckedIndexedAccess": true,
     "noUnusedLocals": false,
     "noUnusedParameters": false,