Host detail v2: full pipeline + per-stage logs + WoL diagnostics

Pipeline now always renders all 13 nodes (3 pre-stage + 9 stage +
Completed), synthesising ghosts from run state when stage rows
aren't seeded yet. Makes a WaitingWoL host show the full timeline
ahead of it instead of just 4 dots.

Agent tags each log line with its stage; logs.Hub fans out to both
log-{runID} and log-{runID}-{stage} SSE events so the detail page
can show per-stage tabs with a pure-CSS radio-sibling switch. Flat
run log prepends [stage] so grep still works.

Dispatcher writes picked/sent-WoL/heartbeat lines into the per-run
log — the operator opens the detail page, sees WaitingWoL stuck,
and reads exactly what the dispatcher did and why nothing's
progressing, instead of having to tail journalctl on the LXC.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/api/agent_handlers.go

@@ -181,6 +181,11 @@ func (a *Agent) Claim(w http.ResponseWriter, r *http.Request) {
 	}
 
 	log.Printf("agent claimed: run=%d agent_ip=%s", runID, agentIP)
+	if a.Logs != nil {
+		if w, err := a.Logs.WriterFor(runID); err == nil {
+			w.Append(logs.Line{Level: "info", Text: fmt.Sprintf("agent claimed from %s — entering Inventory", agentIP)})
+		}
+	}
 
 	// Stage-driven agent needs a bit of per-run config: the device
 	// allowlist (serial + expected size) for Storage, and the iperf3
@@ -331,6 +336,7 @@ type LogBatch struct {
 type LogLine struct {
 	TS    string `json:"ts,omitempty"`    // RFC3339Nano; server clock used if empty
 	Level string `json:"level,omitempty"` // info|warn|error|debug
+	Stage string `json:"stage,omitempty"` // optional stage tag for per-stage log fan-out
 	Text  string `json:"text"`
 }
 
@@ -356,7 +362,7 @@ func (a *Agent) Log(w http.ResponseWriter, r *http.Request) {
 	}
 	for _, l := range batch.Lines {
 		ts, _ := time.Parse(time.RFC3339Nano, l.TS)
-		writer.Append(logs.Line{TS: ts, Level: l.Level, Text: l.Text})
+		writer.Append(logs.Line{TS: ts, Level: l.Level, Stage: l.Stage, Text: l.Text})
 	}
 	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "written": len(batch.Lines)})
 }