docs: rebalance prose cleanup and add trimming skill

docs/rfc/implemented/simplification/2026-06-20-remove-agent-boundary-mirror-events.md

@@ -4,7 +4,7 @@ Status: implemented
 
 ## Problem
 
-The loop exposed durable turn and step boundaries through both `SessionEvent` and live `agent/*` mirrors. Consumers had to choose between two sources for the same fact and reconcile their timing. The stdio UI was the only remaining mirror consumer; ACP and persistence already used the session log.
+The loop exposed durable turn and step boundaries through both the replayable `SessionEvent` log and live `agent/*` mirrors. Consumers had to choose between two sources for the same fact and reconcile their timing. ACP and persistence already used the log; the stdio UI was the only remaining mirror consumer and already rendered tool calls and results from `session/event`.
 
 This duplication is not free. Every lifecycle change had to update the session event, the mirror event, docs, invariants, tests, and snapshot expectations. The duplicate boundary events also made failure ordering subtle: a turn can be durably closed before a live `agent/turn-end` listener runs, so a post-boundary listener failure has no valid in-log position left and must be reported out of band.
 
@@ -12,14 +12,17 @@ This duplication is not free. Every lifecycle change had to update the session e
 
 Make `session/event` the single live boundary/transcript stream. Consumers that render turns, tool calls, tool results, assistant messages, and durable boundaries subscribe to `session/event` and derive their UI from the same event vocabulary persistence uses.
 
-Remove `agent/turn-start`, `agent/turn-end`, `agent/step-start`, and `agent/step-end`. Boundary consumers subscribe to `session/event`. A UI that also needs an agent id maintains a session-to-agent map from `agent/created` and `agent/disposed`.
+Remove `agent/turn-start`, `agent/turn-end`, `agent/step-start`, and `agent/step-end`. Boundary consumers subscribe to `session/event`. A UI that needs an agent label maintains a session-to-agent map from `agent/created` and `agent/disposed`, because the durable `turn/start` carries the turn number but not the agent id.
+
+The step mirrors had no consumers and were removed first by the [event-domain-semantics RFC](../architecture/2026-06-30-event-domain-semantics.md). That decision retained the turn mirrors for the stdio UI; this RFC removes them after migrating that test REPL to `session/event` and the id map.
 
 ## Scope: what is and isn't removed
 
-This decision covers only durable turn and step boundaries. Steering and stream mirrors have separate decisions: [steering](2026-07-04-remove-agent-steering-mirror.md) and [stream chunks](2026-07-02-remove-stream-chunk-mirror.md). `agent/created`, `agent/disposed`, `agent/status`, `agent/error`, and `agent/queued` remain live lifecycle or control events rather than transcript mirrors.
+This decision covers only durable turn and step boundaries. `agent/steering` mirrored a control record and `agent/stream-chunk` mirrored the token stream, so each was handled separately: [steering](2026-07-04-remove-agent-steering-mirror.md) and [stream chunks](2026-07-02-remove-stream-chunk-mirror.md). `agent/created`, `agent/disposed`, `agent/status`, `agent/error`, and `agent/queued` remain live lifecycle or control events rather than transcript mirrors; queued input may be cancelled before any durable event exists.
 
 ## Alternatives considered
 
+- **Remove `agent/steering` in the same change** — rejected because it was a control-record mirror rather than a boundary mirror.
 - **Keep turn mirrors for the stdio UI** — rejected because the UI can render `session/event` and recover the agent label from its id map.
 
 ## Consequences

docs/rfc/implemented/simplification/2026-07-04-drop-image-content-block.md

@@ -18,6 +18,10 @@ Remove `ImageBlock`, its map entry, and image-specific branches from adapters, A
 
 The recorded fallback, had review landed on keeping the slot: keep `ImageBlock` but replace every silent skip with a loud rejection, and document that policy in the vocabulary — the silent drop was the one state with no defender. Review landed on removal; the fallback stands as the documented alternative should the slot ever return ahead of a full feature.
 
+## Verification
+
+No harness `ImageBlock` is constructed outside RFC records. ACP's independent inbound-image rejection remains tested, while adapter, codec, and compaction default branches are covered with plugin-defined block types.
+
 ## Consequences
 
 Re-adding a core vocabulary type later touches several packages at once — but that coordinated change is the shape a real multimodal feature needs anyway (adapter mapping, ACP advertisement, compaction pricing), and none of it existed to preserve.

docs/rfc/implemented/simplification/2026-07-04-fold-stdio-ui-helper.md

@@ -10,7 +10,7 @@ The boundary bought package metadata, workspace and tsconfig references, module-
 
 ## Decision
 
-The `stdio-chat` module now lives inside `dsh-stdio-agent` with its runtime seam and tests. It retains the named Cordis plugin export shape consumed by the app, while keyless Loader smokes cover the composed entry path.
+The `stdio-chat` module now lives inside `dsh-stdio-agent` with its runtime seam. Per-file tests cover EOF, rendering, disposal, and piped-versus-TTY behavior without replacing process globals. It retains the named Cordis plugin export shape consumed by the app; an `unwrapExports` assertion and keyless Loader smokes guard both the package and composed entry paths.
 
 The `packages/support/ui-stdio` package is gone: manifest, tsconfig references, module-graph rows, and README rows deleted; the doc comments that named the package (the example e2e module docs, `packages/README.md`, the support and todo READMEs, [the ui group README](../../../../packages/ui/README.md)) describe the in-package module.
 

docs/rfc/implemented/simplification/2026-07-04-tighten-hook-protocol-contract.md

@@ -21,6 +21,10 @@ Four pieces of the `dsh-hook-protocol`/bridge contract missed the discipline the
 
 Unsupported vocabulary can return when a real consumer exists. `durationMs` remains because durable audit timing is useful independently of a current reader. Bridge-specific payload construction stays in each bridge, while shared durable-event normalization belongs in the protocol library.
 
+## Verification
+
+`HookDialect` contains only Claude and Codex, and `suppressOutput` is absent from source, parsed-field docs, and normalization. `durationMs` remains in events and fixtures with replay scrubbing. The `600_000` and `500` defaults each live once in the protocol library, per-hook timeout overrides still apply, and both bridge suites exercise the library-owned stderr truncation and decision rules.
+
 ## Consequences
 
 The `dialect`, `suppressOutput`, tunables, and semantics changes are invisible on the wire and in the goldens. The cost was churn in `dsh-hook-protocol` and both bridges — cheap under the pre-release stance, and cheaper than letting two copies of a durable event's semantics age apart.

docs/rfc/implemented/simplification/2026-07-04-trim-acp-bridge-unreachable-surface.md

@@ -11,7 +11,7 @@ Two pieces of `dsh-acp` surface were unreachable from any shipped configuration:
 
 ## Decision
 
-Hardcode the existing handshake identity at initialization and remove the unreachable config fields and duplicate defaults. Replace `toolKindFor` with neutral `'other'` at both presenter fallbacks. Normal first-party presentations are unchanged; malformed or failed presentations now render an honest generic card instead of inferring a kind from the tool name.
+Hardcode the existing handshake identity `{ name: 'deepseek-harness-acp', version: '0.0.1' }` at initialization and remove the unreachable config fields and duplicate defaults. Replace `toolKindFor` with neutral `'other'` at both presenter fallbacks. Normal first-party presentations are unchanged; malformed or failed presentations now render an honest generic card instead of inferring a kind from the tool name. Initialize tests and snapshots pin the handshake; only the malformed calls in `hook-codex-posttool-block` change fallback card kind.
 
 ## Alternatives considered