Phase 2 command consolidation: 72 → ~40 slash commands

[BunsDev]

Phase 1 of the deep cut (docs/AUDIT-2026-06.md §4) took the surface from 104 slash-invocable commands to 72. Phase 2 targets ~40 by folding config-ish toggles and the info cluster:

• Fold /vim, /color, /statusline, /terminal-setup into /config subcommands
• Fold /cost + /context into /usage (TUI stats dialog stays reachable)
• Unify /undo / /revert / /rewind into a single rewind UI
• Verify whether the ide named command's integration actually works for coven-code; remove if dead
• Decide fates of /copy vs /export and /chrome, /voice, /advisor placement

Each fold should keep old names as hidden aliases for one release before removal.

[BunsDev]

PR #68 closed this with two bullets incomplete; follow-up in #71:

• Rewind unification — fix(tui): consolidate slash command surface #68 hid /undo//revert but /rewind never absorbed their file-rollback paths, so the capability was hidden-only (and would vanish when the aliases are removed next release). feat(commands): finish #59 remainder — unify /rewind, remove dead ide #71 routes /rewind list|diff|last|<n>|<uuid> to the shadow-git revert paths; bare /rewind keeps the overlay.
• ide verification — verified dead: the command suggests installing coven-code.coven-code, which is not published on the VS Code Marketplace or Open VSX, and no OpenCoven repo ships an editor extension — so the ~/.coven-code/ide/*.lock bridge it reads has no possible writer. Real IDE support is the ACP surface (coven-code acp). feat(commands): finish #59 remainder — unify /rewind, remove dead ide #71 removes the command and the orphaned core::ide module.

Decided placements from #68 stand: /copy, /chrome, /advisor stay visible; /voice folded into /config voice.