feat(guide): Esc interrupts the turn, and the floor is visible [spec 03-03]

[wine-fall]

Implements specs/spec10/10-tui.md (§2.3, §3.4) and specs/spec03/03-03-guide-harness.md (§7) — the conversation-partner boundary, boot-time slice (PR 1 of 2; the mid-broadcast /setup recall is the follow-up and closes #97's reopen gap).

Nine user-pinned decisions from this session's grilling, built:

1. Two identities. The input line always has exactly one partner: the DJ, or the setup guide (a real foreground agent session). The floor rides hello.mode on attach and a new mode message live; the extension rule (at most one foreground agent, identity line names it) is written in spec 10 §3.4 — no framework until a second agent exists.
2. Three-point face change while the guide holds the floor: status strip (in the workshop · the setup guide has the floor), identity line (setup guide · claude), input line (warm ink + talking to the setup guide · esc interrupts · /done hands back). The floor returns the moment the conversation ends — before the closing re-probe, so no line ever queues for the wrong partner.
3. Esc interrupts, never dismisses. Mid-turn: query.interrupt() via the new GuideRequest.onSession handle — the turn dies, the session lives, the next typed line still commands the guide ("continue" finally has an owner). Idle: Esc ends the conversation exactly like /done (the Esc-Esc exit). Before the y: "not now". Only /quit kills the session. No idle timeout.
4. Mechanics: the one-shot stop latch becomes an esc pulse (answers the pending read, re-arms); write_voice_config's abort is armed per call (escEpoch), so a cut noticed mid-validate still cancels that call even after the next turn resets the flow flag.
5. /quit acks instantly: every way a quit begins routes through Director.beginQuit, which prints going off the air... the moment the quit is heard — the ~3s teardown was honest work read as a hang.

Verification

• pnpm test 849 green (new: turn-interrupt loop vs a fake SDK with interrupt(), esc-pulse semantics, the three-state Esc router incl. the mid-validate race and Esc-Esc end-to-end, mode broadcast + late-attach hello, quit acks on all three paths); tsc + oxlint clean.
• Real-SDK smoke (scratch/smoke-turn-interrupt.ts): a guide turn running a 45s tool was cut by interruptTurn() at 5.7s, the SDK answered with the turn's result, the reply loop pulled the next input, and the session answered a second turn. The Esc contract holds at the real boundary.
• Real-TUI pty smoke (pyte, 180×48, stub brain): boot + log flood + Esc regression PASS (pinned ident stands, interrupt reaches the engine as noise safely).
• Peer review (codex gpt-5.6-sol, xhigh): 3 findings, 3 applied (per-call abort watch; floor returned before the closing re-probe; merged-/quit ack), each locked with a regression test.

AI coding brief

• Original request: After the previous fix shipped, the user Esc'd a running install, typed "continue" 17s later, and the DJ answered it as chat — the boundary between talking to murmur and talking to a real code agent was invisible and Esc conflated interrupt with dismissal. A structured grilling produced nine pinned decisions; this PR builds the boot-time slice.
• Manual interventions: The user chose all nine forks (two identities; interrupt-not-end; boot serial; no idle timeout; build mid-broadcast recall next; music keeps playing there; three-point face; rules-not-framework; ack-only quit fix).
• Retro: Grilling before building was the right call — the Esc semantics reversal (kill → interrupt) would have been an expensive re-ship if guessed wrong. The real-SDK smoke of query.interrupt() was the one fact unit fakes could not supply and was worth its tokens.

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