R-856: GET /host/crash-guard — the host crash guard's last-boot record for the controller (09 decision 143)

The controller waits ~15 minutes with app mails after a crash boot of the host; it learns of the
crash boot from this route. Reads /var/lib/felhom-crash-guard/state.json (read-only, no Proxmox call)
and passes present/last_boot_at/last_boot_unclean/tripped through; a missing, unreadable or garbled
file answers 200 present:false. Guest-token authed like every sibling route.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

internal/localapi/server.go

@@ -294,6 +294,9 @@ type Server struct {
 	netMountRoot    string              // the user-data namespace root for the network-mount role gate
 	smbCredsDir     string              // where SMB creds files are written (out-of-band, 0600)
 	escrowStagePath string              // fork-4: 0600 staging file for the pushed restic repo password
+	// crashGuardStatePath (R-856) is the host crash guard's state file read by GET /host/crash-guard;
+	// empty = defaultCrashGuardStatePath. A seam: tests point it at a fixture.
+	crashGuardStatePath string
 	// escrowRecovery (R-199, v0.125.0) assembles chain links 6-8: fetch this host's own sealed
 	// identity blob from the hub, unseal it with the customer's recovery code, return ONLY the
 	// offsite repository password. OPTIONAL — nil (no hub client configured) makes
@@ -520,6 +523,9 @@ func (s *Server) Handler() http.Handler {
 	// Host metrics (slice 9): host-wide health + per-storage capacity for the customer's monitoring
 	// view. Host-wide, token-authed, fresh (a live collect, not the 15-min hub snapshot).
 	mux.HandleFunc("GET /host/metrics", s.withGuest(s.handleHostMetrics))
+	// R-856 (`09` §3 decision 143): the host crash guard's record of the last HOST boot — the controller
+	// waits ~15 min with app mails after an unclean one. Read-only; a missing/garbled file = present:false.
+	mux.HandleFunc("GET /host/crash-guard", s.withGuest(s.handleCrashGuard))
 	// Disk management (slice 8C) — self-scoped; format routes through the data-bearing classifier+gate.
 	mux.HandleFunc("GET /disks", s.withGuest(s.handleDisks))
 	mux.HandleFunc("GET /disks/candidates", s.withGuest(s.handleDiskCandidates))