fix: use temp file for plan checker prompt to avoid E2BIG + fix cancel race condition

The ai-plan-checker.ts was passing the prompt directly as a shell argument,
which can cause E2BIG errors when the terminal buffer is large (8KB+).
This fix applies the same temp file approach already used in ai-idle-checker.ts:
- Write prompt to a temp file instead of passing as shell argument
- Pipe the file to claude via stdin: `cat prompt.txt | claude -p ...`
- Clean up prompt file after check completes

Also fixes a race condition in the cancel() method of both AI checkers where
the poll timer could fire between setting checkCancelled and clearing timers.
Now timers are cleared before resolving the promise to prevent this race.

Includes test utilities and analysis documents for the respawn controller
created by other agents:
- test/respawn-test-utils.ts - MockSession, MockAiIdleChecker utilities
- test/respawn-analysis.md - Code analysis and issue identification
- test/respawn-scenarios.md - Test scenario documentation
- test/respawn-test-plan.md - Testing architecture documentation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -17,7 +17,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 Claudeman is a Claude Code session manager with a web interface and autonomous Ralph Loop. It spawns Claude CLI processes via PTY, streams output in real-time via SSE, and supports scheduled/timed runs.
 
-**Version**: 0.1345
+**Version**: 0.1346
 
 **Tech Stack**: TypeScript (ES2022/NodeNext, strict mode), Node.js, Fastify, Server-Sent Events, node-pty