v0.116.0: observability pass — always-on debug ring + leveled sweep + agent tab + self-log pull — MinAgent: 0.81.0

Capture layer: LogBuffer always exists; logger = MultiWriter(LevelFilterWriter
(stdout, logging.level), ring) so DEBUG detail exists remotely without a config
flip while docker logs keep respecting the level. New internal/logx leveled
helpers. Report ACK gains controller_log_requested (additive); next report
ships controller_log_tail (128KB, consume-once, app-tail wire byte-compatible).
Debug page: Vezérlő|Ügynök tabs; agent tab proxies agent /debug/logs with the
pre-0.83 notice on typed 404. Sweep: netstorage_job phases, netprobe, handler
validation refusals + orphan WARN, SupportsWithSource gate line, agentapi
per-call DEBUG, migrate phase lines, tier2/offbox unswallowed persists.
Red-proofs: filter-disabled, drain-removed, dropped-phase-line all FAIL.

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

controller/internal/web/logbuffer.go

@@ -103,6 +103,47 @@ func (lb *LogBuffer) Entries(minLevel string, limit int, after time.Time) ([]Log
 	return result, total
 }
 
+// Lines renders the held entries as plain text lines (chronological), dropping
+// from the HEAD (oldest) to honor maxBytes so the newest lines survive — the
+// report-channel controller_log_tail budget (maxBytes ≤ 0 → no byte cap).
+// Format mirrors the agent ring's: "<RFC3339> [<LEVEL>] <message>".
+func (lb *LogBuffer) Lines(maxBytes int) []string {
+	lb.mu.RLock()
+	total := lb.size
+	start := 0
+	if !lb.full {
+		total = lb.pos
+	} else {
+		start = lb.pos
+	}
+	entries := make([]LogEntry, 0, total)
+	for i := 0; i < total; i++ {
+		entries = append(entries, lb.entries[(start+i)%lb.size])
+	}
+	lb.mu.RUnlock()
+	lines := make([]string, len(entries))
+	for i, e := range entries {
+		src := ""
+		if e.Source != "" {
+			src = e.Source + ": "
+		}
+		lines[i] = e.Timestamp.Format(time.RFC3339) + " [" + e.Level + "] " + src + e.Message
+	}
+	if maxBytes <= 0 {
+		return lines
+	}
+	budget := 0
+	keepFrom := len(lines)
+	for i := len(lines) - 1; i >= 0; i-- {
+		budget += len(lines[i]) + 1 // +1 for the newline it represents
+		if budget > maxBytes {
+			break
+		}
+		keepFrom = i
+	}
+	return lines[keepFrom:]
+}
+
 // parseLine parses a single log line into a LogEntry.
 func parseLine(line string) LogEntry {
 	entry := LogEntry{