feat(nomos): retry cap, vm: targets, inspect_path, goal supersession, runbooks

Session-review implementation for the three sessions audited in
plans/2026-07-18-session-review-three-sessions.md. v0.7.11 → v0.7.12.

P0.1 — retry cap + investigate-before-retry (cmd/nomos/retrycap.go,
agent.go): after 3 identical failing run calls in a single turn, refuse
to dispatch the call again and return a directive to investigate *why*
(ps/strace/lsof) or surface the blocker. Per-turn scope so a fresh turn
after the operator responds can retry once more. Session 1e9c7691's 20+
identical chown retries (knfsd held a kernel lock on the exported NFS
dir) is the direct motivation.

P0.2 + P1.8 + P2.10 — SOUL.md guidance: hung command is not a failed
command (investigate before retry); ask before proposing a multi-step
migration; multi-goal sessions summarize the arc not just the last goal.

P1.3 — two new runbook entities in seeds/knowledge.yaml:
  - nfs-exported-dir-mutation-hang (the knfsd fchownat lock procedure:
    killall → exportfs -u → mutate → exportfs -a → verify)
  - netbird-mgmt-oidc-race-after-upgrade (docker restart netbird-mgmt
    after ~30s for the traefik/authentik OIDC race)

P1.4 — setGoal emits task.superseded event when prior goal is overwritten
by a different goal (store.go, TestSetGoal_SupersededEvent). Session
55927f0a had two set_goal calls with the first silently abandoned.

P1.5 — inspect_path MCP tool: runs mount/df/ls/stat for one path across
up to 8 targets in one parallel call, replacing the 15+ run-call
fact-gathering fan-out sessions 1 and 2 each spent on cross-target path
tracing (tools.go, server.go: inspectPathAcrossTargets, inspectOneTarget).

P1.6 — vm: target support in run via qm guest exec (no more SSH-hop
with nested quoting). Extracted shared resolveProxmoxHostSlug for
LXC + VM, with hosts-relationship fallback when attributes.host is
absent (server.go, tools.go). Session 55927f0a's SSH-hop workarounds
for vm:zimaos are the direct motivation.

Deferred (documented in plan): P1.7 (approval window auto-extend on
timeout) and P2.9 (long-running command PENDING detection) — both
addressed at lower cost by the retry cap. Session 3's poll-after-timeout
pattern already works; the cap protects against the failure mode.

cmd/nomos/store.go

@@ -492,10 +492,34 @@ func (s *store) taskEntityPtr(ctx context.Context, sessionID string) *uuid.UUID
 // happens — not in reopenSession — because set_goal is the explicit signal
 // for "new sub-task." An approval ("go ahead") does NOT call set_goal, so it
 // won't destroy the plan the operator just approved.
+//
+// P1.4 (2026-07-18): when a non-empty prior goal is being overwritten by a
+// different goal, emit a `task.superseded` event carrying the prior goal.
+// This gives the UI/audit trail a clear signal that the operator pivoted —
+// without it, the prior goal just silently disappears from
+// agent_sessions.goal and there's no record the session ever had a
+// different starting intent. See plans/2026-07-18-session-review-three-
+// sessions.md P1.4 (session 55927f0a had two set_goal calls with the first
+// implicitly abandoned when the operator said "lets just keep ludo-library
+// then").
 func (s *store) setGoal(ctx context.Context, sessionID, goal string) error {
 	if s == nil || sessionID == "" || sessionID == "ephemeral" {
 		return nil
 	}
+	// Capture the prior goal BEFORE the UPDATE overwrites it. If non-empty
+	// and different from the new goal, emit task.superseded so the audit
+	// trail records the pivot — the row's goal column won't.
+	var priorGoal string
+	s.pool.QueryRow(ctx,
+		`SELECT COALESCE(goal, '') FROM agent_sessions WHERE id = $1`,
+		sessionID).Scan(&priorGoal)
+	if priorGoal != "" && priorGoal != goal {
+		_ = observability.Event(ctx, sqlcgen.New(s.pool), "task.superseded",
+			s.taskEntityPtr(ctx, sessionID), "info", "nomos", sessionID,
+			map[string]any{"prior_goal": priorGoal, "new_goal": goal})
+		slog.Info("nomos: task goal superseded by a new set_goal",
+			"session", sessionID, "prior_goal", priorGoal, "new_goal", goal)
+	}
 	// Replace any prior plan steps (done/running/pending/...) as `replaced`.
 	// The rows are kept for the generation counter + audit trail; proposePlan
 	// excludes `replaced` from its in-flight check, so the next propose_plan
@@ -868,7 +892,7 @@ type staleGoalSession struct {
 }
 
 // staleGoalSessions finds sessions that framed themselves as a real task
-// (goal != '', so the inline safety net in agent.go intentionally left them
+// (goal != ”, so the inline safety net in agent.go intentionally left them
 // alone) but have sat non-terminal past idleThreshold. completion_nudges
 // tells the caller whether to nudge (0) or give up and auto-close (>=1) —
 // see processIdleSweep in continue.go.