Feature: /opencode:verify command for checking plans, trackers, prior output

[JohnnyVicious]

Motivation

Users want a way to ask OpenCode "did this actually get done?" against a tracker, checklist, or prior OpenCode output — a verification pass, not a fresh review. Today you'd have to hand-craft a /opencode:rescue prompt for every verification.

Proposed UX

/opencode:verify --tracker TODO.md
/opencode:verify --plan path/to/plan.md
/opencode:verify --last    # verify the diffs produced by the last task run

Modes:

• --tracker <file>: read the tracker file, compare against the current tree, report which items are actually done.
• --plan <file>: check that the plan's listed changes exist in the tree / git history.
• --last: use the last task job's changedFiles + result summary and ask OpenCode to verify the claimed changes were actually made and work.

Implementation sketch

• New command plugins/opencode/commands/verify.md.
• New handler handleVerify that constructs context from the tracker/plan/prior-job data and runs the standard review flow under the plan agent.
• Reuse jobDataPath to load the previous job's result when --last is used.

Upstream reference

Derived from openai/codex-plugin-cc#10.