feat(sse,tui): bump spec pin to v0.29.0 + AwaitingLlmFirstToken (v0.14.0)

Spec pin moved da93ca7 (v0.28.0) → 562001a (v0.29.0); vendored
conversation-api-spec.md + conversation_api.contract.md re-snapshotted.
The only material delta is Worldtree #201's awaiting_llm_first_token
SSE heartbeat — a top-level event (NOT a worker_phase extension, per
INV-053's three-field stability) that fires at a configurable interval
(default 5s) during the BuildingPrompt → CallingLLM gap.

Wire layer (sse_client.py):
- New `AwaitingLlmFirstToken` dataclass: sse_id / turn_id /
  elapsed_ms_since_building_prompt (server-authoritative monotonic)
- Added to Event union + _envelope_for_type dispatch branch
- Without this, ratatoskr would crash on any slow-first-token turn
  from a v0.29.0 server (unknown SSE event type → ValueError)

TUI layer (tui.py):
- Audit pipeline: per-event debug-pane line with elapsed in seconds
- Live transcript indicator: first heartbeat mounts a Static
  ("awaiting first token · 5.0s"); subsequent heartbeats update it
  in place; any non-heartbeat event removes it (the gap closed)
- Turn-summary line now carries heartbeat count
- Indicator demoted via .awaiting-label CSS so it reads as ambient
  progress, not content

Tests: 2 wire-layer (single + monotonic sequence) + 3 presenter
(audit line shape, single-mount semantic, indicator removal on gap
close). Suite: 318 passing.

docs/conversation_api.contract.md

@@ -1881,6 +1881,73 @@ SQLite `consumer_agents` table.
   through `_publish`, so SSE resume / replay handles them with no
   special case.
 
+## Amendment — AwaitingLLMFirstToken heartbeat (issue #201, INV-201-1..7)
+
+Adds a periodic SSE heartbeat event during the gap between
+`BuildingPrompt` and `CallingLLM` so consumers can distinguish
+"engine is thinking" from "engine is wedged" without out-of-band
+server inspection. Filed by ratatoskr-dev; ships in v0.29.0.
+
+- **INV-201-1 (new top-level event type)**: `awaiting_llm_first_token`
+  is a new top-level SSE event type, sibling to `worker_phase` /
+  `tool_*` / `text` / `thinking` / `debug` / `done` / `affect_update`.
+  `_WORKER_PHASE_VOCAB` is NOT extended; INV-053 / INV-054 unchanged.
+  Same precedent as #204's `affect_update`.
+
+- **INV-201-2 (config-gated emission)**: Heartbeat emission requires
+  `awaiting_llm_first_token_heartbeat_s > 0.0`. When the resolved
+  value is `0.0`, the heartbeat task is never started and zero
+  `awaiting_llm_first_token` events emit for the turn. When > 0.0,
+  the task starts immediately after `_publish_phase("BuildingPrompt")`
+  and emits an event every `interval` seconds until cancelled.
+
+- **INV-201-3 (defense-in-depth cancellation)**: The heartbeat task
+  is cancelled at three sites (idempotent via the `_cancel_heartbeat`
+  helper): (a) immediately before `_publish_phase("CallingLLM")` on
+  the engine-first-event path; (b) inside the `cancelled`/`error`
+  handling that wraps `_handle_cancel` (covers stall + user-cancel
+  paths); (c) in the outer `finally` block alongside
+  `_clear_stall_timer`. After cancellation, no further
+  `awaiting_llm_first_token` events emit.
+
+- **INV-201-4 (wire shape)**: Payload is exactly `{type:
+  "awaiting_llm_first_token", turn_id: <int>,
+  elapsed_ms_since_building_prompt: <float>}` plus the composite `id:
+  "<turn_id>:<seq>"` stamped by `_publish`. No additional fields.
+  `elapsed_ms_since_building_prompt` is `(time.monotonic() -
+  building_prompt_t) * 1000.0` where `building_prompt_t` is captured
+  immediately before `BuildingPrompt` is published.
+
+- **INV-201-5 (first-gap-only scope)**: Heartbeat is scoped to the
+  FIRST `BuildingPrompt → CallingLLM` gap of the turn. Tool round-trip
+  `CallingLLM` re-entries (INV-058) emit ZERO
+  `awaiting_llm_first_token` events. Out-of-scope sub-phases
+  (`AwaitingToolResult`, `AwaitingNextLLMCall`) would be separate
+  follow-up features.
+
+- **INV-201-6 (replay participation)**: Heartbeat events flow through
+  `_publish → _replay_buffer + queue` per INV-060 — same replay
+  semantics as worker_phase events. On `Last-Event-ID` reconnect,
+  prior heartbeats replay identically.
+
+- **INV-201-7 (config resolution precedence)**: Per-agent
+  `agent.conversation.awaiting_llm_first_token_heartbeat_s` →
+  `api_cfg.awaiting_llm_first_token_heartbeat_s` → built-in `5.0`.
+  Negative values raise `ConfigurationError` at agent load; `0.0`
+  is valid and means "disabled." Mirrors the `_resolve_stall_timeout_s`
+  precedence pattern (INV-038).
+
+### Mechanism note
+
+The heartbeat task is a separate `asyncio.Task` (NOT `loop.call_later`,
+because heartbeats repeat at an interval rather than fire once at a
+timeout). An `asyncio.Queue` shared between the heartbeat task and the
+generator carries events; the generator uses
+`asyncio.wait(return_when=FIRST_COMPLETED)` to race the engine's
+`__anext__` against the heartbeat queue's `get` ONLY during the first
+iteration. After `CallingLLM` fires, the heartbeat task is cancelled
+and subsequent iterations use the original non-race pattern.
+
 ### Storage extension
 
 The `consumer_agents` table lives in `core/heimdall/storage/sqlite.py`