Add Brella networking domain skill

[alexph-dev]

Summary

• Add a Brella / white-label event networking domain skill.
• Document observed web URLs, API endpoints, event join behavior, networking state endpoints, attendee extraction, and dedicated browser profile guidance.

Why

• Reuses known Brella workflow details instead of rediscovering join/API/networking mechanics each time.

Validation

• Ran git diff --check origin/main..HEAD.
• No runtime tests; documentation-only domain skill.

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Summary by cubic

Adds a Brella/white‑label event networking domain skill to standardize how we join events, query APIs, and extract attendee data. This is documentation-only and reduces repeated discovery work.

• New Features
  • Web and white‑label URL patterns (next.brella.io, <org>.brella.io).
  • API endpoints for public event lookup, invite prefill, and join; note brella-organization-slug header and WRONG_APP behavior.
  • Networking state: me‑attendee GET/PUT, onboarding completion, and skip-networking caveat.
  • People extraction via /api/events/<event-slug>/attendees with pagination/search, JSON:API joins, and curl --globoff.
  • Browser harness guidance for a dedicated profile and CDP port.

^{Written for commit f6561bd. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}