Adds an opt-in review gate flow to annotation mode with three composable flags:
- `--gate`: 3-way UX (Approve / Send Annotations / Close)
- `--json`: structured decision output (`{"decision":"approved|annotated|dismissed"}`)
- `--silent-approve`: suppresses plaintext approve marker for naive hooks
Includes shared arg parser, @-reference handling, updated templates across all
harnesses (Claude Code, Copilot, Gemini, OpenCode, Pi), and full documentation.
Closes#570
For provenance purposes, this commit was AI assisted.
Michael Ramos