A fifth ExitPlanMode approval choice — sits between the existing
"Approve and execute" (purge session) and "Approve and keep context"
(full transcript). Runs `handleCompactCommand` against the plan-mode
transcript with a planning-specific custom instruction rendered from
`plan-mode-compact-instructions.md`, then dispatches the plan-approved
synthetic prompt so it lands as the first entry in the freshly-
summarized transcript — giving execution a fresh cache anchor with
the rationale carried over.
Cancel/fail contract:
- ok → bookkeeping runs, plan-approved synthetic prompt dispatched.
- cancelled → bookkeeping runs (tools restored, plan reference path
recorded), warning surfaced, dispatch skipped.
`markPlanReferenceSent` is intentionally deferred past
the cancel guard so `AgentSession.#buildPlanReferenceMessage`
re-injects the plan on the operator's next prompt() call.
If we marked it sent on cancel, the executor's first turn
would have no plan context.
- failed → bookkeeping runs, error already surfaced by executeCompaction,
dispatch proceeds best-effort. Approval intent stands.
Cancel vs. fail is discriminated via `instanceof CompactionCancelledError`
at the session/compaction error boundary (introduced in the previous
commit), so any abort source — operator Esc, extension hook, programmatic
abort — classifies uniformly without input-modality or message-string
coupling.
Op: extend
cognitive
0eb8d0fdcd