[BUG] `deadreckon doctor` fails under a non-C locale with "checkpoint pid … has a different process-start identity"

[maxalbert]

• Deadreckon Version: 0.8.4 (from source)
• OS: macOS 15.7.7, launchd supervisor agent

Symptom

deadreckon doctor --repair is blocked:

supervisor service: failed - ... checkpoint pid 3874 has a different process-start identity

The supervisor is running normally; only the checkpoint validation reports a problem.

Root cause

process_start_identity() (crates/deadreckon-core/src/exec/pid_file.rs) builds the macOS start identity from /bin/ps -p <pid> -o lstart=, which is locale-dependent.

• The instance.json checkpoint is written by the launchd-spawned supervisor, which runs under C locale (no LANG/LC_ALL).
• doctor run from a user shell recomputes the identity under the shell locale (e.g. LANG=en_GB.UTF-8).

Same running process, different rendering — the byte-for-byte comparison in validate_checkpoint_identity() fails:

Locale	ps -p 3874 -o lstart=
C / unset (supervisor)	Fri Aug 7 06:47:56 2026
en_GB.UTF-8 (doctor)	Fri 7 Aug 06:47:56 2026

The function is documented as a "stable same-boot identity", but the macOS implementation is locale-dependent, violating that guarantee. doctor --repair cannot self-heal because the repair loop re-evaluates the same comparison.

Reproduction

# fails
LANG=en_GB.UTF-8 deadreckon supervisor status --json
# passes
LANG=C deadreckon supervisor status --json
LANG=C deadreckon doctor --repair

Suggested fix

Pin the ps subprocess to the C locale in process_start_identity(), e.g. .env("LANG","C").env("LC_ALL","C"), or read a locale-independent start token (e.g. proc_pidinfo/kern.proc), matching the Linux branch's /proc/<pid>/stat field 22.