fix(pi): sync bash prompt with the fence

[apc5074]

Problem

Closes #894.

Pi agents were getting stuck on a few things that should work:

• Agents thought they could not remove .posthog-events.json, even though scoped rm is allowed.
• Agents were unsure when new events did not show up in read-data-schema yet.
• Valid quoted paths like app/(main)/page.tsx were blocked because they contain parentheses.

Changes

• Updated the pi runtime notes to mention scoped rm and .posthog-events.json cleanup.
• Added shared guidance that new events may not appear in read-data-schema until they are ingested.
• Allowed parentheses inside quoted bash arguments, while still blocking real shell syntax.
• Made pi task mode use the same scoped rm boundary as linear pi runs.
• Added regression tests.

Test plan

• pnpm exec vitest run src/lib/__tests__/wizard-can-use-tool.test.ts src/lib/agent/runner/harness/pi/__tests__/runtime-notes.test.ts src/lib/agent/runner/harness/pi/__tests__/security.test.ts src/lib/agent/__tests__/commandments.test.ts
• pnpm build
• pnpm test
• pnpm fix