Bring test files and fixtures into typecheck scope

[TheGreatAxios]

Closes CL-5759.

Verified the gap was real

tsconfig's include was src/**/*.ts and packages/**/*.ts only — tests/, evals/, and scripts/ (159 test files) were outside it. Confirmed empirically: introduced a type error in src/state.test.ts (caught by tsc --noEmit) and the same kind of error in tests/unit/plugin-repo-locator.test.ts (not caught), then reverted both.

Fix

Widened include to add tests/**/*.ts, evals/**/*.ts, scripts/**/*.ts. Excluded, by name, only the capability eval suite's hermetic sandbox repos under tests/fixtures/** and all of evals/capability/cases/** — these are copied into per-run eval workdirs rather than imported by our code, own their own package.json, and tests/fixtures/buggy-service deliberately ships a bug as fixture content for an eval case.

Two fixture directories are deliberately not in that exclusion list, even though they live under tests/fixtures/: tests/fixtures/crash-run and tests/fixtures/plugins/implement-feature. Both import real production modules by relative path (src/index.ts, src/session/active-run.ts, src/session/state.ts, src/tui/runner.ts, src/workflows/definition.ts, src/tui/commands/registry.ts) and tests/integration/crash-finalize.test.ts spawns crash-run's scripts as live exercises of that code — excluding them would recreate exactly the silent-drift gap this PR closes. Typechecking implement-feature surfaced a real instance of that drift: its relative import paths were two directories short (stale since the fixture was last touched), so import type { CommandPlugin } from "../../../src/tui/commands/registry.js" resolved nowhere. Fixed the path depth; the fixture isn't wired into any test today, so this was invisible until now.

bun run typecheck (tsc --noEmit) is unchanged, so the wider scope runs in the same command contributors already use.

Errors surfaced

116 pre-existing errors across ~28 files, plus the two broken import paths above. All fixed properly, none suppressed:

• Real field/signature drift caught by the widened scope: LastCycleSource.id → sourceId, AgentProfile.prompt → systemPromptRole, ApprovalScope gaining required id/label, StringToolHandler now requiring an AbortSignal argument, InboundMessage's actual wire shape (not the informal {role, content} a test assumed), ProviderSettings.baseURL becoming required, PricingFetcherOptions.fetchImpl over-typed as typeof fetch (which also demands static members like preconnect that no test double implements, narrowed to a plain call signature), and the two stale relative-import paths in tests/fixtures/plugins/implement-feature described above.
• Routine noUncheckedIndexedAccess/exactOptionalPropertyTypes fallout in test helpers (array-index access, optional-field passthrough), fixed with non-null assertions or conditional-spread construction where the code's own logic already guarantees the value.
• Narrow, commented casts only where a test deliberately needs a loose shape (e.g. casting a whole mock event object rather than just its data field, since a partial cast on data alone doesn't line up with the surrounding discriminant).

Full test suite (bun test ./src ./tests ./evals) passes: 5281 tests, 0 failures. bun run check passes in full.

Noticed but not touched

Nothing else in scope needed suppression or a config relaxation.

[linear-code]

CL-5759