fix(agent): refuse plan re-proposal + emit done on error (close divergence chain)

Operator-reported bug: on 'proceed with the rest' the agent re-proposed the
plan, duplicating it in the sidebar. Root cause was a three-bug chain, not
one bug:

1. Trigger — model empty-response on 'proceed' (approval vocabulary didn't
   list 'proceed', so the agent wasn't sure it was approved and no-op'd).
2. Amplifier — chatWith emitted 'error' without 'done' on empty response
   (agent.go:370). The frontend's onComplete saw !receivedDone and
   misclassified the model failure as a network disconnect, calling
   handleDisconnect -> resumeSession.
3. Divergence — the reconnect note was generic ('report your state'), so
   the agent re-proposed + re-executed instead of advancing the plan.

Fixes (shipped, e2e-validated against the live agent on oikos-nomos-1):

- A.2: proposePlan refuses re-proposal once a step has started (returns
  errPlanInFlight). Drops the append-mode safety net (commit 5384499) that
  was the direct source of the sidebar duplication. The agent must advance
  with update_plan_step + run; the tool result directs it.
- A.1: proposePlan sets the 'generation' column on INSERT (migration 020
  added the column + frontend grouping, but the INSERT never wired it).
- A.3: propose_plan tool description restated as a crisp contract (ONCE,
  STOP and wait, REFUSES once a step started, advance with update_plan_step).
- F.3: approval vocabulary expanded to approved/yes/go/proceed/continue/ok/
  go ahead; propose_plan result string tightened to an imperative.
- B.1: chatWith emits 'done' after 'error' on every terminal path via a new
  emitError helper. The frontend now treats model errors as ended (not
  disconnected), so no auto-reconnect -> resumeSession fires.
- B.2: reconnect/resume note carries the operator's last message + an
  explicit 'advance the plan, do NOT call propose_plan again' directive when
  a plan is in flight. Wired into all 4 resume entry points (reconnect,
  /resume, idle-sweep, question-answer) via enrichResumeNote.
- B.3: resumeSession escalates the recovery note across its 3 attempts (final
  retry: 'pick the lowest-pending step, mark it running, call run — do that
  now') instead of 3 identical notes -> 3 identical empties.

Verification: TestProposePlan_RefuseInFlight replaces TestProposePlan_
AppendVsReplace. e2e conversations against the rebuilt container:
  conv2 ('proceed with the rest') -> 0 propose_plan calls, plan stayed at
    3 steps (was 6+ before), update_plan_step x5 + run x2 + complete_task.
  conv3 (full plan, 'go ahead') -> apt-get update on lxc:dns auto-ran under
    the plan window, update_entity_attributes writeback, clean complete_task.
  nomos logs show zero reconnect/resume entries for the plan-proposing
    sessions (the three-bug chain is closed).

Remaining (not in this commit): D.1 refuse complete_task without writeback
(next blocker), C.1/C.2, F.1/F.2 SOUL.md consolidation, B.4-B.6, E.1/E.2.
See plans/2026-07-14-post-fix-session-remainders.md.

Also: re-audit 2026-07-10-general-gated-execution.md — request_execution enum
retirement (60effcb) closes item 9; only auto-act revival (item 10) remains.

Version 0.4.1 -> 0.5.0 (minor: new structural behavior, not a bugfix).

plans/2026-07-10-general-gated-execution.md

@@ -1,13 +1,17 @@
 # 2026-07-10 — General gated execution: from fixed actions to unlimited-but-gated
 
-**Status:** In Progress — audited 2026-07-11. Done: `ClassifyCommand` risk
+**Status:** In Progress — re-audited 2026-07-14. Done: `ClassifyCommand` risk
 classifier, general `run` MCP tool, chat-assent approval (no button
 required), blast radius on approval cards, session digest, global activity
 feed (`Ops.svelte` "Executions" tab, risk-badged), Learning view
-(success-rate trend). Still open: retire the fixed `request_execution`
-action enum (`restart, systemctl, pct_exec, apt_upgrade, pct_create` still
-hard-coded alongside `run`), and revive auto-act — `internal/actuator/actuator.go:125`
-is still a literal `{"success": true, "message": "stub execution"}` stub.
+(success-rate trend), **and now the `request_execution` enum retirement**
+(commit `60effcb`, 2026-07-14 — `run` is the only mutation tool; the legacy
+handler functions are kept as reference only, with a "DO NOT re-register"
+guard in `internal/mcp/server.go:360`). Still open: **revive auto-act** —
+`internal/actuator/actuator.go:~125` is still a literal
+`{"success": true, "message": "stub execution"}` stub (item 10). The
+`run`-gated path covers operator-initiated work end-to-end; auto-act is the
+observe→Act direction (signals triggering actions), still unimplemented.
 
 ## Goal