Unify SQLite busy baseline

[zccz14]

Summary

• Configure every openTaskDatabase() SQLite connection with the shared busy/WAL baseline: busy_timeout, WAL journal mode, synchronous=NORMAL, and foreign keys.
• Remove the optimizer lane events local busy timeout because the shared database opener now owns that baseline.
• Add a behavior test that opens a real task database and verifies the persisted PRAGMA behavior instead of source shape.

Tests

• pnpm install --ignore-scripts
• pnpm exec vitest run --config vitest.workspace.ts --project api modules/api/test/task-database.test.ts (RED: failed with busy_timeout 0 before implementation, then passed)
• pnpm --filter ./modules/contract run build:dist (explicit prerequisite for package exports)
• pnpm exec vitest run --config vitest.workspace.ts --project api modules/api/test/task-database.test.ts modules/api/test/optimizer-lane-events.test.ts modules/api/test/task-repository.test.ts modules/api/test/manager-state-repository.test.ts modules/api/test/coordinator-state-repository.test.ts modules/api/test/dimension-repository.test.ts modules/api/test/opencode-session-repository.test.ts
• pnpm --filter ./modules/api run typecheck
• pnpm --filter ./modules/api run test:lint
• pnpm --filter ./modules/api run test:vitest