fix(tui): a null message_id on the first hook fire must not disarm the F1 guard

Residual found by the independent reviewer's second pass, by PROBING the fixed code rather
than reading it — the F1 fix was correct but its ARMING could be skipped entirely.

TuiDeltaAssembler.messageId was initialized to `null`. A first MessageDisplay payload carrying
message_id:null therefore compared EQUAL to the sentinel, registered no boundary, and left
`messages` at 0. When the real boundary then arrived, `else if (this.messages > 1)` evaluated
1 > 1 === false, so restartedAfterEmit never armed, and the `released` branch forwarded the
auth banner to the client — the exact leak F1 closed, reachable again through a single null
field. parseDeltaChunk does not validate message_id, so such a payload does reach push().

Two changes, both narrowing:
  - messageId now initializes to a Symbol sentinel, which is === to nothing a JSON payload can
    produce, so the first fire ALWAYS registers as message 1 whatever its message_id is.
  - the boundary branch drops the `this.messages > 1` sub-condition. It bought nothing and was
    the sole cause. The real invariant is "a boundary occurred while emitted !== ''" — which is
    unrecoverable regardless of how many messages have been seen — and that is now what the
    code says.

Whether claude ever emits message_id:null is unverified (the observed contract has it present),
so this is defense-in-depth, not a live bug. But the guard is the mechanism this feature
nominates as its primary safety property; it should not be disarmable by a field's absence.

Mutation-tested: restore the null sentinel + the messages>1 condition and the new test fails;
with the fix, 317 passed / 0 failed (was 316).

Class B (ADR 0007, OCP-owned TUI spawn) — cli.js does NOT perform this operation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VqgWJcjxrjjL9L9SkpZyXR

README.md

@@ -24,7 +24,7 @@ One proxy. Multiple IDEs. All models. **$0 API cost.**
 
 There are several Claude proxy projects. OCP picks a specific lane: **align tightly with what `cli.js` actually does, observe + multiplex what's already there, don't extend the protocol.** What you get:
 
-- **LAN multi-user keys** (v3.7.0) — reach one Claude Pro/Max subscription from your own devices across the LAN. Each device gets a per-key API token (no OAuth session leak), with independent usage tracking and one-line revocation. Pro/Max are **per-user** accounts — see [Sharing with family / a team — honest limits](#deployment-model--security-read-this) before extending access to other **people**.
+- **LAN multi-user keys** (v3.7.0) — share one Claude Pro/Max subscription with family, friends, or your own devices. Each user gets a per-key API token (no OAuth session leak), with independent usage tracking and one-line revocation.
 - **`ocp-connect` one-shot IDE setup** — one command on the client machine detects and configures Claude Code, Cursor, Cline, Continue.dev, OpenCode, and OpenClaw. No pasting `OPENAI_BASE_URL` six times.
 - **Response cache with per-key isolation + singleflight** (v3.13.0). Optional SHA-256 prompt cache, isolated per API key (cross-user pollution is impossible by hash construction, not by application logic), with stampede protection on concurrent identical prompts. Off by default. ([PR #65](https://github.com/dtzp555-max/ocp/pull/65), [PR #66](https://github.com/dtzp555-max/ocp/pull/66))
 - **Per-key request quotas** (v3.8.0). Daily / weekly / monthly limits per key — set a kid's iPad to 20/day, a partner's laptop to 100/week. ([PR #18](https://github.com/dtzp555-max/ocp/pull/18))
@@ -49,7 +49,7 @@ OCP and the alternatives serve adjacent but distinct needs. Pick the one that fi
 | GitHub stars / ecosystem size | small | large | mid |
 | Governance discipline (CI-enforced alignment with cli.js) | yes | n/a | n/a |
 
-**Plain English**: `claude-code-router` is the routing-and-switching power tool — pick it if you want to mix Anthropic, OpenAI, Gemini, and local models behind one endpoint. `anthropic-proxy` is the minimal forwarder. **OCP focuses on disciplined `cli.js`-aligned forwarding plus subscription multiplexing** — pick it if you want to reach one Claude Pro/Max subscription from your own IDEs and devices, with LAN auth, quotas, and a governance contract that prevents endpoint drift.
+**Plain English**: `claude-code-router` is the routing-and-switching power tool — pick it if you want to mix Anthropic, OpenAI, Gemini, and local models behind one endpoint. `anthropic-proxy` is the minimal forwarder. **OCP focuses on disciplined `cli.js`-aligned forwarding plus subscription multiplexing** — pick it if you want to share one Claude Pro/Max subscription across IDEs, devices, and people, with LAN auth, quotas, and a governance contract that prevents endpoint drift.
 
 ### Related: OLP — Open LLM Proxy
 
@@ -215,7 +215,7 @@ After install the `ocp` CLI lives at `~/ocp/ocp`. To put it on your PATH, either
 export OPENAI_BASE_URL=http://127.0.0.1:3456/v1
 ```
 
-**LAN mode** — reach OCP from your own devices on the network (Claude Pro/Max are per-user accounts — see [Sharing with family / a team — honest limits](#deployment-model--security-read-this) before extending access to other people):
+**LAN mode** — share with other devices on your network:
 ```bash
 # Enable LAN access with per-user auth (recommended)
 node setup.mjs --bind 0.0.0.0 --auth-mode multi