v0.83.0: observability pass — always-DEBUG capture ring + GET /debug/logs + heartbeat log-pull + gap-fill sweep

Capture layer: applog.New returns (logger, Ring) — slog fan-out, stderr at the
configured level, ~1000-entry ring fixed at LevelDebug (remote diagnostics
without a config flip). GET /debug/logs (token-authed, ?raw=1) + request-level
DEBUG middleware. Heartbeat log-pull mirrors the report logtail pattern:
envelope log_tail_requested -> next heartbeat carries log_tail (128KB cap,
consume-once, failed-push retry proven). Gap-fill sweep over netverify/
netstorage/netmount/signedjobs/selfupdate/disks/controller-swap/desired/loop.
Red-proofs: ring-at-emit-level FAILs capture test; drain removed FAILs
consume-once; dropped phase line FAILs the S7 log-sequence smoke.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

internal/localapi/debuglogs.go

@@ -0,0 +1,64 @@
+package localapi
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	applog "gitea.dooplex.hu/admin/felhom-agent/internal/log"
+)
+
+// GET /debug/logs (v0.83.0 observability) — the agent's always-DEBUG capture ring,
+// served over the same token-authed, self-scoped local API as every sibling route.
+// This is what makes the agent's side of a flow (e.g. a NAS verify) visible from the
+// controller's Debug page without journald access or a config flip. ?raw=1 mirrors
+// the controller viewer's plain-text variant. Log lines carry keys never values
+// (logging conventions), so the ring is safe to serve to the guest's operator view.
+
+// handleDebugLogs serves the ring as JSON entries ({entries, total}) or plain text.
+func (s *Server) handleDebugLogs(w http.ResponseWriter, r *http.Request, vmid int) {
+	if s.logRing == nil {
+		writeErr(w, http.StatusServiceUnavailable, "debug log ring not configured on this agent")
+		return
+	}
+	limit := 0 // 0 = everything held (ring-bounded)
+	if v := r.URL.Query().Get("limit"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil && n > 0 && n <= applog.DefaultRingSize {
+			limit = n
+		}
+	}
+	if r.URL.Query().Get("raw") == "1" {
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		for _, line := range s.logRing.Lines(0) {
+			w.Write([]byte(line))
+			w.Write([]byte("\n"))
+		}
+		return
+	}
+	entries, total := s.logRing.Entries(limit)
+	writeOK(w, map[string]any{"vmid": vmid, "entries": entries, "total": total})
+}
+
+// statusRecorder captures the wrapped handler's status for the request log line.
+type statusRecorder struct {
+	http.ResponseWriter
+	status int
+}
+
+func (sr *statusRecorder) WriteHeader(code int) {
+	sr.status = code
+	sr.ResponseWriter.WriteHeader(code)
+}
+
+// logRequests is the request-level DEBUG middleware: method, path, status, duration
+// — never bodies (bodies can carry secrets; the ring must not).
+func (s *Server) logRequests(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+		rec := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
+		next.ServeHTTP(rec, r)
+		s.logger.Debug("local-api: request",
+			"method", r.Method, "path", r.URL.Path,
+			"status", rec.status, "duration_ms", time.Since(start).Milliseconds())
+	})
+}