Add /yolo slash command to toggle skip-permissions live

[TheGreatAxios]

Summary

Adds a /yolo slash command that toggles --dangerously-skip-permissions for the rest of the session, with a clear status flash and transcript notice.

Closes CL-6297.

Changes

• /yolo flips live skipPermissions via the permission gate
• Status/transcript feedback when enabling or disabling
• Wired through built-in command registry (same surface as other session toggles)

Test plan

• Targeted unit/command tests green in worktree
• Pre-commit typecheck + build on commit
• Manual: /yolo enables skip-permissions; consequential tools do not ask
• Manual: /yolo again disables; asks resume
• Manual: does not affect auto-mode envelope

[linear-code]

CL-6297

[TheGreatAxios]

Reviewed as reviewer of record against CL-6297.

Verdict: approve (GitHub will not let this identity formally approve its own PR).

/yolo is a live twin of the CLI skip-permissions flag: it flips setSkipPermissions on the existing gate and pre-gate sandboxes consult a getter, so outside-workspace access unlocks (or re-locks) without rebuilding plugins.

Checked:

• Command: /yolo, /yolo on, /yolo off; bare invocation toggles. Missing context (exec) returns not available in this mode.
• Enable message states the envelope: gate bypassed, secret-guard and authz remain.
• Envelope holds: secretGuardPlugin and authzPlugin sit before permissionPlugin and do not read skip-permissions. Gate evaluate() early-returns the same way the CLI flag already does.
• Live sandbox consult: pathEscapePlugin, deleteFilePlugin, shellGuardPlugin / persistent cwd, and list_dir all take allowOutside: () => permissionGate.getSkipPermissions().
• Tests cover command on/off/toggle/unknown/unwired, gate live toggle, and per-call allowOutside getters.
• ARCHITECTURE / IMPLEMENTATION / PRODUCT (secret guard, path sandbox, recovery) mention /yolo.

Nits (not blocking):

• Ticket listed an explicit toggle argument. Handler treats only empty args as toggle and rejects toggle with Usage: /yolo [on|off]. Easy follow-up if you want the ticket text to be literal.
• PRODUCT.md's built-in slash-command list still omits /yolo even though nearby paragraphs mention it.

Commit message is plain English and matches the change.