refactor: tsconfig missing noUnusedLocals/noUnusedParameters/noUncheckedIndexedAccess

[dean0x]

Problem

tsconfig.json lacks several TypeScript compiler flags that would improve type safety and catch common mistakes:

• noUnusedLocals — detect unused local variables
• noUnusedParameters — detect unused function parameters
• noUncheckedIndexedAccess — require index bounds checking

These flags are currently not enabled.

Current Status

• Pre-existing: identified in feat/flags-typed-registry review (2026-08-25)
• Repo-wide impact: enabling these flags surfaces ~9 dead-import fixes
• Scope outside this PR: 6 additional fixes needed outside the PR's diff, e.g., src/cli/commands/init.ts

Suggested Sequencing

From review feedback:

1. Enable noUnusedLocals + noUnusedParameters first (cheaper wins, fewer ripples)
2. Then enable noUncheckedIndexedAccess behind its own separate change (requires more careful fix work)

Acceptance Criteria

• tsconfig.json enables noUnusedLocals
• tsconfig.json enables noUnusedParameters
• All existing tests pass with new flags
• Dead imports cleaned up where flags surface them
• Optional future work: noUncheckedIndexedAccess in a separate change

Related

• PR feat(flags): typed flag registry, settings-page TUI, new upstream flags #300 (feat/flags-typed-registry)
• Source: typescript.md review finding, 2026-08-25