docs(mesh): Phase 2 live-gate record + correct the buffer-size rationale

Flipped the docker-dev rig end-to-end to MeshTransport:Mode=ClusterClient
(OTOPCUA_MESH_MODE, no rebuild) and ran the gate. PASSED for the transport:
deploy seals on ClusterClient, a stopped node fails the deploy naming it, the
MaintenanceMode hatch shrinks the DB-sourced contact set live (6->5->6 on both
centrals independently), and the frame-size canary stayed silent.

Four findings, recorded in 2026-07-22-mesh-phase2-live-gate.md:

  A. A 10-30s post-restart delivery window exists, but the DPS control fails
     identically -- it is a cluster-convergence property, not a Phase 2
     regression. Running the control is the only reason this is a note and not
     a false attribution.

  B. buffer-size=0's stated rationale was OVERSTATED. A node applies a TimedOut
     deployment anyway -- live-observed at +44s -- via DriverHostActor.Bootstrap
     replaying the orphan Applying row on restart. Zero buffering removes the
     silent, timer-driven replay, not the boot-time DB one. Corrected in the
     plan decisions table, Configuration.md, and CLAUDE.md; the decision stands,
     the justification narrowed.

  C. Stopping BOTH centrals strands the non-seed nodes at the Akka membership
     layer (frozen mid-Exiting, not Unreachable, so auto-down does not help).
     Transport-independent; a Phase 7 downing/rejoin drill item.

  D. The AdminUI driver Restart/Reconnect buttons (DriverStatusPanel) are
     rendered by no page -- orphaned since v3 Batch 2 retired /clusters/{id}/
     drivers. So gate steps 6/7 could not run; the driver-control node-side leg
     is proven live only because DispatchDeployment shares its EventStream path.

Step 8's planned log-signal does not exist (HandleApplyAck is silent on
success); proven instead by both centrals independently logging per-instance
ClusterClient creation, which a singleton cannot.

Also adds a repo-root .dockerignore: docker-dev/Dockerfile does COPY . ., which
was pulling .claude/worktrees (19GB of agent checkouts with their own bin/obj)
into the build context and exhausting the Docker VM disk mid-COPY.

Rig restored to Mode=Dps, six members, no leftover maintenance flags.

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

docs/plans/2026-07-22-mesh-phase2-clusterclient-transport.md

@@ -15,7 +15,7 @@
 | Decision | Choice | Why |
 |---|---|---|
 | Cutover | **Config-flagged dark switch** (`MeshTransport:Mode` = `Dps` default \| `ClusterClient`) | Lets the rig gate A/B the same deploy and roll back with a config change, not a revert. Phase 1's live gate is the argument: the defect only appeared against real infrastructure. |
-| Buffering | **`buffer-size = 0`** (drop immediately) | Akka's default buffers 1000 and replays on reconnect. With Phase 1 semantics a deploy recorded `TimedOut` would still be applied minutes later when the node returns — the node runs a config the DB says failed. Fail-fast keeps the DB the single record of truth. |
+| Buffering | **`buffer-size = 0`** (drop immediately) | Akka's default buffers 1000 and replays on reconnect. With Phase 1 semantics a deploy recorded `TimedOut` would still be applied minutes later when the node returns — the node runs a config the DB says failed. Fail-fast keeps the DB the single record of truth. **CORRECTED by the live gate ([finding B](2026-07-22-mesh-phase2-live-gate.md)):** this justification was overstated. A node applies a `TimedOut` deployment *anyway*, via `DriverHostActor.Bootstrap()` replaying the orphan `Applying` row on restart (live-observed at +44 s). `buffer-size = 0` removes the *silent, timer-driven* replay, not the boot-time DB one. The decision stands; the rationale narrowed. |
 | `alarm-commands` central leg | **In scope** | Same shape as driver-control; leaves no half-migrated command plane. The topic stays alive for the node-local publisher. |
 
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