feat(x): add guest mode for repository questions (#165354)

feat(x): add guest mode for repository questions (#165354)

* feat(x): add guest mode for repository questions

Allow public mentions through an explicit guest switch while deriving sender
tiers only from numeric X user IDs and the effective maintainer allowlist.
Keep guest tools limited to repository reads and listings, isolate each guest
mention from maintainer session state, and retain revocation fences.

Add bounded atomic daily author quotas, smaller guest thread context, quoted
post data, administrator config persistence, and guest readiness/status in
X replies. Preserve maintainer work sessions and omit their links from guest
replies. Document filesystem prerequisites and keep subagent tools excluded.

* fix(x): include guest settings in bundled config metadata