The SDK's buildExecutorPrompt told executors to "Create a SUMMARY.md file"
with no directory path, causing them to write it in cwd (project root)
instead of .planning/phases/{phase}/. Thread phaseDir from PhaseRunner
through PromptFactory and into the completion instructions so the executor
gets an explicit path like `.planning/phases/01-auth/01-01-SUMMARY.md`.
Backward compatible — buildExecutorPrompt still accepts a plain string
(agentDef) for existing callers.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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