docs(prd): fold 2026-07-09 debate-pass findings into Mosaic Platform PRD

All 24 panel findings (P0#1-5, P1#6-13, P2/P3#14-24) accepted and folded:
- DEBATE-FINDINGS.md: disposition record + open-disagreement judgment calls
- north-star: NS-14, J2a/J2b split, J6 wake router, K3 push pipeline,
  M1 memory subsystem, workstream L (MALS lineage), real DAG edges
- J: workspace lease J-R16, resume protocol J-R18, write-side trust,
  needs-decision lifecycle, atomic card publish
- P: CAS approval state machine, gateway-only credentials, default-closed
  gating, principal resolution + policy snapshot (Codex #2/#7)
- W: butt-in exclusive lease, structured control plane, break-glass
  doctrine, trial metric panels
- Q: external_refs table, pending-link, echo-loop guard, crash barriers
- X: storage authority (Postgres sole record), machine-generated census,
  memory retrieval-eval retirement gate, honest rollback scope,
  4 artifact-existence machine gates, bounded day-30 review
- README: Gate Zero, conflict register, DoD line, silent-roster rule

One item OPEN for Jason at ratification: gate superstructure (§3.1).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RMoEx7hfdFGjUiCHuN1RRi

docs/fleet/proposals/mosaic-platform-prd/PRD-webui-fleet-control.md

@@ -2,6 +2,7 @@
 
 > **Status:** DRAFT for ratification · **Goals:** W1–W3 · **Upstream anchor:** `PRD-fleet-suite.md` Phase F6 ("webUI hooks — stable JSON contract + terminate/attach(butt-in) surface")
 > Confirmed gap: zero xterm/pty/tmux code in `apps/web` on either the old snapshot or `origin/main`.
+> **Debate pass 2026-07-09:** panel findings folded — see `DEBATE-FINDINGS.md`.
 
 ## Mission
 
@@ -35,11 +36,22 @@ The user can pop in on **any** agentic tmux session from the web, and get a full
 | W-R10 | Operator controls: PAUSE kill-switch (NS-8), per-agent terminate (killswitch service), queue pause/resume — each gated + audited; destructive controls confirm.          |
 | W-R11 | Existing widget framework (`AgentStatusWidget`, `OrchestratorEventsWidget`, SSE proxy routes) is the starting point, upgraded to the fleet contract rather than rebuilt. |
 
+## Debate-accepted deltas (2026-07-09) — normative
+
+| ID    | Requirement                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
+| ----- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| W-R12 | **Butt-in is an exclusive lease** with explicit, visible takeover: at most one interactive holder per session at any instant; a second client must take the lease and both parties see the transfer. Input frames are sequenced and deduped so a reconnect never double-sends; a heartbeat/idle timeout closes both the lease and its audit span — audit spans always terminate (extends W-R1/W-R3/W-R4).                                                                         |
+| W-R13 | **Structured control plane:** PAUSE, terminate, restart, approve/deny, and queue operations are typed API verbs with RBAC and audit — never bytes typed into a tmux pane. Raw terminal input via butt-in is **rescue-only** and a separately-grantable permission from the control verbs.                                                                                                                                                                                         |
+| W-R14 | **Break-glass doctrine (documented, not prevented):** SSH + `tmux attach` on the fleet host bypasses W1 and P **by design**; it is inventoried under P-R19, audited post-hoc from host logs, and never treated as a product path. PAUSE additionally has an **on-host file/CLI actuator** so a dead gateway can never lock the operator out of the control that fixes the gateway.                                                                                                |
+| W-R15 | W3 ships the **trial metric panels** as workspace-scoped product views over product storage: canary machine-flag correctness, approval decision latency, card priority distribution, wake→ack rate, agent-authored memory retrieval fraction, human interaction load, fixed-input probe stability. The X-R9 trial evidence pack cites these panels; until W3 exists, day-1 emission targets MALS (L1). Workspace isolation fixture: workspace-2 admin sees zero workspace-1 rows. |
+
 ## Acceptance criteria
 
 1. From a browser (desktop + phone), the user watches a live coder-agent pane read-only, then butt-ins with the right grant, types a message, detaches; agent session continues; audit log shows both.
 2. Dashboard reflects an agent crash within one heartbeat interval; PAUSE flip halts dispatch within one tick (AC-NS-5) from the UI.
 3. A user without butt-in grant can watch but cannot type (enforced server-side).
+4. Two clients contend for butt-in: exactly one holds the lease at any instant, the takeover is visible to both, and after a forced reconnect the input stream shows zero duplicated or interleaved frames (W-R12).
+5. With the gateway stopped, the operator PAUSEs the fleet via the on-host actuator; the bypass appears in the post-hoc audit (W-R14).
 
 ## Non-goals