Merge worktree-hooks-b-bash-seam into worktree-hooks-c-interception

Bring the interception-seams branch onto current master (via A→B). The
substantive reconciliation is master's compaction `agent/pre-step` serial seam
meeting C's interception seams:

- types.ts: keep BOTH master's `agent/pre-step` AND C's new interception events
  (`agent/prompt-submit`, `agent/session-start`, `agent/turn-continuation`→
  `ContinuationDecision`); drop the turn-mirror declarations (removed on A).
- loop.ts: the merged per-turn order is `turn/start` → per queued msg
  `agent/prompt-submit` (rewrite/inject/block) → (fully-blocked ⇒ zero-step
  `rejected`) → per step: drain steering → assemble system prompt →
  `agent/pre-step` (compaction, OUTSIDE the step) → `step/start` → single
  `deriveMessages()` → model → tools/pre-execute·dispatch·post-execute. No
  turn-mirror emits; `closeTurn()` is the A-simplified single-call form.
- Docs (architecture, core.md, agent/agent-loop READMEs, catalog) reconciled to
  show C's interception seams alongside `agent/pre-step`, no turn/step mirrors.
- rfc/README: dropped the stale `proposed/` compaction row (master moved that RFC
  to implemented/); kept C's new `pre-tool-input-rewrite` proposed row.
- interception.spec.ts: migrated its two `agent/turn-end` reason collectors to
  the `turn/end` session event, and ADDED a cross-test proving a
  `prompt-submit` rewrite + additionalContext is VISIBLE to an `agent/pre-step`
  listener on the same turn — pinning the merged seam ordering (compaction sees
  the post-prompt-submit surface, not stale history).

packages/ui/acp/README.md

@@ -57,7 +57,7 @@ When the client does NOT advertise the capability, none of the `_meta`/terminal
 
 ## Settle-exactly-once
 
-A `session/prompt` resolves (or rejects) exactly once, keyed off the canonical session log (the `session/event` stream), NOT the `agent/turn-start`/`agent/turn-end` events. One listener captures the prompt's owning turn from the log's `turn/start` and settles on the matching `turn/end` — the one signal that always fires (`closeTurn` appends it unconditionally, even when a boundary emit throws and the `agent/turn-end` EVENT is skipped). A prompt settles only on ITS OWN turn (`inflight.turn === turn/end.turn`), so a stale `turn/end` for a previously-cancelled turn whose end arrives late can never settle the wrong prompt. A turn that ends `error` REJECTS the RPC with an internal error carrying the failure message (ACP has no error stop reason); every other reason resolves via the codec. As a fallback, when the agent settles to `idle`/`disposed` with a prompt still pending — e.g. a `session/event` listener registered before the bridge threw and starved the bridge's listener — an `agent/status` handler reconciles the prompt from the log (the owning turn's `turn/end`, or `cancelled` if the turn was torn down without one). An empty/whitespace prompt is rejected up front — it would queue no work, so no turn would start and the RPC would hang.
+A `session/prompt` resolves (or rejects) exactly once, keyed off the canonical session log (the `session/event` stream). One listener captures the prompt's owning turn from the log's `turn/start` and settles on the matching `turn/end` — the durable boundary event (`closeTurn` appends it unconditionally; there is no `agent/*` turn mirror). A prompt settles only on ITS OWN turn (`inflight.turn === turn/end.turn`), so a stale `turn/end` for a previously-cancelled turn whose end arrives late can never settle the wrong prompt. A turn that ends `error` REJECTS the RPC with an internal error carrying the failure message (ACP has no error stop reason); every other reason resolves via the codec. As a fallback, when the agent settles to `idle`/`disposed` with a prompt still pending — e.g. a peer `session/event` listener registered before the bridge threw and starved the bridge's listener — an `agent/status` handler reconciles the prompt from the log (the owning turn's `turn/end`, or `cancelled` if the turn was torn down without one). An empty/whitespace prompt is rejected up front — it would queue no work, so no turn would start and the RPC would hang.
 
 ## Disposal & disconnect
 

packages/ui/acp/src/index.ts

@@ -199,13 +199,14 @@ interface SessionRecord {
 }
 
 /**
- * Drive the in-flight prompt's settle from the harness event stream. A turn
- * can end three ways the bridge must all handle (AGENTS.md "honor cross-seam
- * contracts on BOTH sides"): the normal `agent/turn-end` event; a `turn/end`
- * session event WITHOUT the agent event (a boundary emit threw inside the loop,
- * which still appends `turn/end`); or the agent erroring/settling to idle. The
- * first of these to fire settles the prompt; `settle` is then cleared so the
- * others are no-ops (settle-exactly-once).
+ * Drive the in-flight prompt's settle from the harness event stream. The bridge
+ * settles off the durable log: the `turn/end` session event on the
+ * `session/event` feed for the prompt's own turn, with the agent
+ * erroring/settling to idle as a fallback (AGENTS.md "honor cross-seam contracts
+ * on BOTH sides") for the case where a throwing peer `session/event` listener
+ * starved the bridge's listener before it saw the boundary. The first of these
+ * to fire settles the prompt; `settle` is then cleared so the others are no-ops
+ * (settle-exactly-once).
  */
 export function apply(ctx: Context, config: AcpConfig): void {
   // TODO(double-default): these literals duplicate the Config schema defaults
@@ -318,15 +319,14 @@ export function apply(ctx: Context, config: AcpConfig): void {
   // the canonical log: every assistant/chunk and tool/call/result is logged, so
   // translating from the log makes live streaming and `session/load` replay
   // share the identical path (streamSessionEventUpdate). Both the owning-turn
-  // capture and the settle key off the log's own `turn/start`/`turn/end` — NOT
-  // the `agent/turn-start`/`agent/turn-end` EVENTS, which a throwing PEER
-  // listener (cordis `emit` stops at the first throw) or a boundary-emit failure
-  // can skip. `closeTurn` appends `turn/end` to the log unconditionally, and
-  // `turn/start` is appended before any step runs, so within this one listener
-  // we always see the prompt's turn-start (tag `inflight.turn`) then its
-  // turn-end (settle). A `turn/end` settles the prompt ONLY when it is the
-  // prompt's OWN turn (`inflight.turn === event.data.turn`) — a previous,
-  // already-cancelled turn whose end arrives late is ignored (see
+  // capture and the settle key off the log's own `turn/start`/`turn/end` — the
+  // durable boundary events (there is no agent/* turn mirror). `closeTurn`
+  // appends `turn/end` to the log unconditionally, and `turn/start` is appended
+  // before any step runs, so within this one listener we always see the
+  // prompt's turn-start (tag `inflight.turn`) then its turn-end (settle). A
+  // `turn/end` settles the prompt ONLY when it is the prompt's OWN turn
+  // (`inflight.turn === event.data.turn`) — a previous, already-cancelled turn
+  // whose end arrives late is ignored (see
   // SessionRecord.inflight). A turn that ends `error` REJECTS the prompt (ACP
   // has no error stop reason); other reasons resolve via the codec. Demux
   // strictly by session id: a `session/event` is routed to its own record, so