[Task] Make goal-finish human review handoff idempotent

[StatPan]

Goal

Make gira goal finish --terminal human_review --apply idempotent so repeated runs do not post duplicate goal-finish-receipt/v1 handoff comments for the same terminal state.

Parent: #521

Scope

Detect an existing goal-finish-receipt/v1 comment on the goal issue before planning or applying the human-review handoff. Dry-run should report a skip/no-op action when the receipt already exists, and apply should not post another comment. The command should keep preserving blockers and should not close the goal.

Acceptance Criteria

• Dry-run reports an already-present/skipped handoff action when a goal receipt exists.
• Apply is idempotent and does not post a second goal-finish-receipt/v1 comment.
• JSON exposes whether the handoff receipt already exists.
• Tests cover dry-run no-op, apply no-op, and first apply comment posting.
• Docs mention that human-review goal finish apply is idempotent.

Doctor Impact

No doctor behavior expected.

Expected Evidence

• go test ./internal/gira
• go test ./internal/cli
• go test ./...

Expected Delivery

Draft PR first, then normal Gira review/finish lifecycle.

base_branch: main
base_source: branch_policy.default
branch_policy_mode: github-flow
target: default
work_branch: issue-588-task-make-goal-finish-human-review-handoff-idempotent

[StatPan]

Finish Receipt

• Finished at: 2026-05-23T04:19:08Z
• Ticket: [Task] Make goal-finish human review handoff idempotent #588 status=Done state=closed
• Linked PR: feat: [Task] Make goal-finish human review handoff idempotent #589 state=MERGED merged=true
• Checks: passed total=11 passing=11 pending=0 failing=0
• Review: unknown
• Evidence: closing_reference,branch_binding,checks
• AI Delivery Telemetry: not_required
• Label changes: add=status:done remove=status:in-review
• Warnings: incomplete_acceptance_criteria
• Next: ticket is done