fix(terminal): drop stale terminal_output chunks after a reconnect race

[RonenMars]

Summary

Investigated a Terminal-tab bug where displayed conversation lines appeared shuffled.
useTerminalStream.ts trusts raw WebSocket arrival order to feed its client-side VT100 emulator (virtual-terminal.ts) — normally reliable, but a reconnect can leave a stale terminal_output frame from the superseded connection in flight, and it can land after the client has already reset state for a fresh terminal_replay, landing content out of order.

The companion streamer PR (threadbase-streamer#299) adds a per-session monotonic seq to terminal_output/terminal_replay. This PR consumes it here: a lastSeqRef guard drops any terminal_output chunk whose seq isn't greater than the last accepted one, and terminal_replay.seq baselines it on (re)subscribe.

• Additive/backward compatible: a streamer that omits seq (older version) never trips the guard — msg.seq != null gates both checks.
• No change to wrapping behavior (confirmed separately: that's native RN Text wrap, working as intended).

Base branch note

Branched from fix/diff-viewer-full-width-lines-integration (currently the most recent upstream branch) since basing off main directly produced Podfile.lock rebase conflicts from unrelated iOS build-number bump commits already on that branch. This PR's own diff touches only hooks/useTerminalStream.ts, services/ws-client.ts, and its new test file — no overlap with the base branch's changes.

Test plan

• npx tsc --noEmit — clean
• npx eslint hooks/useTerminalStream.ts services/ws-client.ts __tests__/unit/hooks/useTerminalStream.seq.test.tsx — clean
• New __tests__/unit/hooks/useTerminalStream.seq.test.tsx: accepts increasing seq, drops a stale/lower seq, baselines from terminal_replay.seq, and never rejects when a streamer omits seq entirely
• Existing useTerminalStream.userMessages.test.tsx and useTerminalStream.watchdog.test.tsx still pass (14/14 total across the three suites)