docs: add the friends and family beta runbook

[Chris0Jeky]

Outcome

Adds the missing operator and participant runbook for GH-1325 without creating a new beta backend, invite UI, telemetry path, or hosted-product claim.

The runbook recommends the existing hardened maintainer-hosted two-account private instance for the first guided participant, while retaining the packaged Windows workspace as the privacy-preserving alternative when the participant should own all local data.

What the runbook covers

• composes STAGE1_PRIVATE_INSTANCE_RUNBOOK.md rather than duplicating or weakening its identity-policy, backup, restore, registration-closure, provider-budget, and evidence contracts
• gives a browser-only hosted invitee journey with exact Register, Inbox, Review, Approve, Apply-to-board, and confirm-Apply steps
• gives a per-device Windows path grounded in the current 0.3.x Windows quick start, checksum, SmartScreen, loopback, data, stop, backup, and update contracts
• states plainly that the maintainer can access a hosted instance's database/backups
• explains that a maintainer-owned OpenAI key means the maintainer pays and captured content egresses under the maintainer's provider account
• chooses one private shared note plus trusted direct contact as the cohort feedback channel; participants do not need GitHub
• defines manual activation milestones, first-independent-loop and return-use evidence, plus the weekly five-minute check-in
• routes redacted findings into the standing dogfooding lane and preserves the intake-severity exemption without granting automatic priority
• includes withdrawal, shutdown, uncertain-write, data-loss, and security incident procedures
• keeps the final GEN-11: Friends & family beta channel - runbook, invite path, feedback loop, activation metrics #1325 walkthrough as an explicit remaining acceptance gate

Current-source reconciliation

The original issue predated several now-shipped prerequisites. This runbook is grounded in current main at 2cdc4525766101211fe04787e23bfb46b6aa4011:

• the Windows first-run, quick-start, and durable app-data work is delivered
• the private-instance Stage 1 contract now provides a stricter two-account boundary, identity policy, encrypted backup, fresh-volume restore drill, registration-closure proof, and provider budget
• the current packaged path is Windows 10/11 x64 with the 0.3.x quick start
• current builds do not provide a non-GitHub cohort feedback sink, so this slice makes an explicit zero-backend channel decision instead of claiming one exists

Scope and authority

• One new documentation file: docs/ops/FRIENDS_FAMILY_BETA.md
• No runtime, schema, dependency, workflow, registration, provider, telemetry, or authorization change
• No change to STATUS.md, the masterplan, current product direction, or test totals because shipped reality did not change
• No personal identity, invite code, provider key, access URL, database content, or private feedback is committed

Verification

• fetched the created file back from the branch after publication
• manually reconciled every repository-relative link against current paths
• copied the exact invite command, registration order, backup/restore boundary, and provider disclosure from current canonical runbooks
• copied the Windows execution and review sequence from the current Windows quick start
• GEN-11: Friends & family beta channel - runbook, invite path, feedback loop, activation metrics #1325 remains open: the required maintainer or clean-container/VM walkthrough has not been performed or invented
• node scripts/check-docs-governance.mjs and node scripts/check-doc-links.mjs remain required on the PR head; this connector session has no executable current-main checkout from which to run them locally

Part of GH-1325.