src/, scripts/ and bench/ carry no unused imports or locals: `tsc --noUnusedLocals` finds nothing there #4740

Measured on main at d0a2ee1d: bun x tsc --noEmit --noUnusedLocals reports 129 unused imports, locals and types (TS6133/6192/6196), about 70 of them outside test/. Many are leftovers from the §5 design moves, for example helpers a page imports and no longer calls. They make every review read dead code, and the gate cannot catch the next one until they are gone.

Done:

• [ ] bun x tsc --noEmit --noUnusedLocals 2>&1 | grep -v '^test/' reports no TS6133, TS6192 or TS6196. The biggest files are src/web/studio/asks.ts, src/web/pages/{repo,pull,issues}.ts, src/tui/screens/pull.ts and src/crew/autonomy.ts; about 45 other files have one or two findings each.
• [ ] Removal only: no behaviour changes. An unused function parameter that is part of a handler signature is prefixed _, not removed. An export is never removed by this issue.
• [ ] bun x tsc --noEmit, bun scripts/design-lint.ts and the tests of the touched modules pass.

Risk: open pulls touch some of these files. Keep each edit to the import or local line so a rebase stays trivial.