Migrate implement-ticket repository review remediation to review-fix-loop

[shaug]

Outcome

Migrate implement-ticket to delegate its repository review/remediation loop to the packaged review-fix-loop skill without changing ticket lifecycle or acceptance ownership.

Design: design/review-fix-loop.md
Related epic: #95

This is an intentionally separate fast follow, not a subissue of #95.

Scope

• Map the caller's existing review/fix behavior, authority, and outputs onto the standalone invocation and terminal-result contracts.
• Preserve implement-ticket ownership of ticket scope, acceptance, PR readiness, and lifecycle decisions.
• Add compatibility and regression coverage for interrupted and piecemeal implementation.

Non-goals

• Changing review-fix-loop to absorb ticket lifecycle responsibilities.
• Migrating other callers.

Acceptance criteria

• The caller uses the standalone skill for repository review/remediation.
• Caller-owned acceptance and lifecycle behavior remain explicit and unchanged.
• Every terminal state has a tested caller mapping.
• Exact-head validation and review evidence remain trustworthy after delegation.
• Existing implement-ticket evaluations continue to pass, with new migration coverage.

Dependency

Blocked by the packaged-skill leaf of #95.