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

.gitignore

@@ -40,6 +40,8 @@ pnpm-debug.log*
 
 # TypeScript
 *.tsbuildinfo
+# tsc emit artifacts — Vite handles compilation, tsc is type-check only
+packages/web/src/**/*.js
 
 # Misc
 .cache/