Persist yolo as the user-global skip-permissions default

[TheGreatAxios]

Summary

• /yolo (on/off/toggle) writes skip-permissions as the user-global default so later sessions start in that stance without --dangerously-skip-permissions
• The launch flag still forces skip-permissions for that process; secret-guard and authz hard blocks still apply
• Default stays off until the operator turns YOLO on once

Verification

• bun run typecheck and bun run build pass
• bun run test: 4990 pass; 2 fail in grok-4.6 reasoning-effort cycling (unrelated to this change; those tests expect high → low, implementation advances to xhigh)
• Config tests cover settings seed without the flag, flag override of settings false, and exec inheriting the persisted default

Fixes CL-6685

[linear-code]

CL-6685

[TheGreatAxios]

https://linear.app/abklabs/issue/CL-6685/persist-yolo-as-a-global-default-not-session-only

[TheGreatAxios]

Self-review

Verdict: ship with should-fix. No blocking functional defect in the diff. /yolo live-flips then persists as the user-global default; next launch seeds from settings without the flag; --dangerously-skip-permissions still forces this process on. Secret-guard and authz are untouched.

Should-fix

1. Persist wrap is untested. Schema and loadConfig seed are covered; /yolo → saveGlobalSettings is not. Missing: on writes true, off writes false, unreadable settings still live-flips and notices.
2. /yolo off is unproven on the read path. Round-trip tests only use true. Merge is flag || settings?.dangerouslySkipPermissions === true.
3. Exec inherits the sticky default with no --no-…. After /yolo on, later corbits exec skips the gate. docs/PRODUCT.md still says exec fail-closes unless the CLI flag is set — that paragraph is now wrong.

Nits

• Success copy does not mention persist.
• Persist is unsynchronized RMW; overlapping /yolo vs other persistGlobalSettings callers can last-write-win.
• --config TUI /yolo writes the override file, not ~/.corbits/settings.json (same as compaction / showPromptCost).
• No CHANGELOG Unreleased note for a user-facing safety default.
• CommandContext JSDoc still says “for the rest of the session”.

Will land these in a follow-up commit on this PR.