fix(pi): wait for terminal assistant response in RPC mode

[SamuelLHuber]

Problem

When PiAgent runs in RPC mode, Smithers could finalize the session on the first assistant turn_end even when PI was still continuing internally through tool use and subsequent turns.

Observed behavior

• PI sessions that used tools could appear to finish early
• long-running implementation tasks could look idle, truncated, or schema-only
• Smithers could miss the true terminal assistant response

This made PI-backed tasks unreliable in the exact cases where RPC mode is most useful: longer, tool-using sessions.

Fix

• update PI RPC completion handling so Smithers does not finalize on assistant turn_end events whose stopReason is toolUse
• continue listening until the real terminal assistant answer arrives
• finalize from the later terminal turn or agent_end
• preserve existing behavior for simpler single-turn PI sessions

Docs / samples

• add a minimal runnable sample at examples/pi-hello-world.tsx
• add a second runnable sample at examples/pi-tools-workflow.tsx that uses PI tool calls (read and bash)
• add a brief PI docs pointer showing how to run the sample and how to discover available PI models (models.json / pi --list-models)

Why this approach

PI tool-use sessions are multi-turn conversations. Treating the first assistant turn_end as final is too eager. The minimal safe fix is to keep the RPC session open across tool-use turns and only finalize once PI reaches a true terminal assistant state.

Validation

• bun test tests/pi-support.test.ts
• bun run cli run examples/pi-hello-world.tsx
• bun run cli run examples/pi-tools-workflow.tsx

Added focused coverage for:

• standard PI RPC prompt/response flow
• RPC extension UI requests
• tool-use RPC sessions that continue past an intermediate turn_end and only finish on the final assistant answer
• JSON mode extraction behavior already covered by existing PI tests

Observed sample results:

• examples/pi-hello-world.tsx returned {"message":"hello world"}
• examples/pi-tools-workflow.tsx successfully used tools and returned the expected structured output, including:
  • phrase: "saffron-orbit-lantern"
  • lineCount: 3
  • cwdBasename: "examples"

Scope

This PR intentionally contains only:

• the minimal PI RPC completion fix
• two minimal PI runnable samples
• a brief PI docs note

No trace capture or observability changes are included in this branch.

🤖 Generated with pi / smithers