#requestAcpPlanApprovalChoice returned 'value !== REFINE_OPTION' which
treats any non-refine outcome — explicit dismissal, transport failure,
abort, or timeout — as approval. That meant closing the elicitation
dialog (or the request failing) granted the agent write access without
explicit user consent.
Tighten to 'value === APPROVE_OPTION' so only the explicit approve
selection passes the gate. Refine, dismissal, and every other outcome
fall through to refine semantics: the caller keeps plan mode active and
returns guidance text instead of renaming the plan and exiting.
Adds a regression test that drives a form-capable harness with a
cancelled elicitation and asserts the plan file is preserved, plan
mode/handler stay active, plan reference stays unset, and no mode-exit
notifications are emitted.
