Phase 2 core slice of #91277: the updater now knows WHAT it is operating
on before it mutates anything.
- hermes_cli/update_inventory.py (new): side-effect-free runtime
inventory — install kind via detect_install_method (git / docker / nix
/ apt, updatable-in-place or not, with the correct external update
command for image/package-managed installs), all profiles, every live
gateway with its supervisor (systemd / launchd / manual via the
fleet-wide _get_service_pids), running code_sha/code_version from the
#91283 gateway_state.json stamps, and the restart mechanism each
runtime will get.
- hermes update --plan: prints the plan and exits; runs BEFORE the
docker/nix refusal gates so image-managed installs get a useful
'not updatable in place + right command' report instead of a bare
refusal. Read-only, safe on a live fleet.
- Every real update run now records the pre-update plan in its receipt
('plan' key) and prints a one-line fleet summary, so post-mortems can
compare what the update SAW against what it did.
- Docs: updating.md (--plan section + receipts/fleet-check section),
cli-commands.md (flag row + receipts behavior bullet).
- 11 tests: two-profile fleet classification, docker not-in-place,
dead-PID exclusion, PID-file fallback dedupe, all-probes-fail
never-raises, JSON round-trip for the receipt, print output shapes,
receipt integration.