Every stop hook fire spawned a new background `mempalace mine` via
subprocess.Popen with no dedup — 4 concurrent mines at ~770% CPU
observed in production. Add `_mine_already_running()` (reads
`hook_state/mine.pid`, uses `os.kill(pid, 0)` as an existence check)
and `_spawn_mine()` (writes the child PID to the lock file after
Popen returns). `_maybe_auto_ingest` bails early when the guard
reports True.
Tests: 4 new unit tests for `_mine_already_running` (no file, dead
PID, live PID using `os.getpid()`, corrupt file), 1 new test
covering the skip-when-running branch of `_maybe_auto_ingest`, and
existing spawn tests patched to redirect `_MINE_PID_FILE` into
tmp_path so they don't touch the real state dir.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
jp
a6b6e55247