[AI-assisted] docs(copilot): describe the transcript journal, not the removed dual-write mirror (#125599)

* docs(copilot): describe the transcript journal, not the removed dual-write mirror

The new copilot plugin doc described transcript persistence through
extensions/copilot/src/dual-write-transcripts.ts with session-scoped
content-fingerprint keys and best-effort failure containment. That module
was removed in #114403 (Jul 27): attempts now own an
attempt-transcript-journal keyed by run id and SDK event id, journaled in
structurally complete groups, and persistence failures fail closed by
aborting the SDK session and flagging replay as unvalidated.

Rewrite the section around the current journal, and update the two
"transcript mirror" references that pointed at it.

* docs(copilot): clarify invalid replay starts a fresh session

Co-authored-by: Santhi Prakash <b.santhiprakash@gmail.com>

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

docs/plugins/copilot.md

@@ -13,7 +13,7 @@ OpenClaw's built-in harness. The Copilot CLI session owns the low-level
 agent loop: native tool execution, native compaction (`infiniteSessions`), and
 CLI-managed thread state under `copilotHome`. OpenClaw still owns chat
 channels, session files, model selection, dynamic tools (bridged), approvals,
-media delivery, the visible transcript mirror, `/btw` side questions (see
+media delivery, the visible chat transcript, `/btw` side questions (see
 [Side questions (`/btw`)](/plugins/copilot#side-questions-%2Fbtw)), and `openclaw doctor`.
 
 For the broader model/provider/runtime split, start with
@@ -228,22 +228,32 @@ When `harness.compact` runs, the Copilot SDK harness:
 3. Returns the SDK compaction outcome without writing compatibility marker
    files under the workspace.
 
-The OpenClaw-side transcript mirror (below) keeps receiving post-compaction
+The OpenClaw-side transcript journal (below) keeps receiving post-compaction
 messages, so user-facing chat history stays consistent.
 
-## Transcript mirroring
+## Transcript persistence
 
-`runCopilotAttempt` dual-writes each turn's mirrorable messages into the
-OpenClaw audit transcript via
-`extensions/copilot/src/dual-write-transcripts.ts`. The mirror is scoped per
-session (`copilot:${sessionId}`) and keyed per message
-(`${role}:${sha256_16(role,content)}`), so re-emitted prior-turn entries
-collide with existing on-disk keys instead of duplicating.
+`runCopilotAttempt` gives each attempt a transcript journal
+(`createAttemptTranscriptJournal` in
+`extensions/copilot/src/attempt-transcript-journal.ts`) that persists every
+turn's messages into the OpenClaw session transcript. Journal identity is
+turn-scoped, not content-scoped: the initial user turn is keyed
+`${runId}:user` and SDK-sourced events are keyed
+`copilot-sdk:${sdkSessionId}:${eventId}`, with claimed event ids plus an
+idempotency scan at the transcript store, so re-emitted prior-turn entries
+cannot duplicate.
 
-Two layers of failure containment wrap the mirror so a transcript write
-failure never fails the attempt: an internal best-effort wrapper, plus a
-defense-in-depth `.catch(...)` at the attempt level. Failures are logged, not
-surfaced.
+Assistant turns and their tool results are journaled as structurally complete
+groups, so a crash between groups leaves a valid transcript prefix.
+`before_message_write` hooks may redact content but cannot change role or
+tool topology; a structurally destructive rewrite suppresses the whole group
+instead of persisting a false replay.
+
+Persistence failures fail closed. The first write failure marks the journal
+failed, aborts the in-flight SDK session, and flags the attempt's replay as
+unvalidated so the next run creates a fresh SDK session instead of trusting a
+partial transcript. Only the post-append transcript update notification is
+best-effort and logged.
 
 ## Side questions (`/btw`)