The OpenCode plugin's forge command gains `plan`: show the planner's wave and nod or redirect it #5322

For: the same one-line steering of the plan from OpenCode as from Claude Code.

Done:

• [ ] plugins/opencode/forge.ts's COMMAND text gains plan [approve|redirect <words>|later], worded as the Claude Code command is: asks → first wave-proposal row → asks_proposal, applied only after the person says yes.
• [ ] plugins/opencode/README.md says how to use it.
• [ ] A case in test/plugins.test.ts checks the OpenCode command names asks_proposal and that the tool exists; it fails without the change.

Files: plugins/opencode/forge.ts, plugins/opencode/README.md, test/plugins.test.ts. Risk: the Claude Code plan issue edits test/plugins.test.ts too; add a separate describe block.