Guide admins to confirm onboarding source repos after value

[Gandy2025]

What changed

• Teach first-tree-welcome to preserve repo provenance: declared team source vs ad-hoc path/URL.
• After the first verified onboarding result, ask a confirmed admin once whether the resolved GitHub repo should become a team source repo.
• Keep the write deliberate: the agent shows the exact candidate and directs a positive choice to Settings → GitHub → Source repos; it never writes a team resource or calls agent-private agent config add-repo.
• Order the repo confirmation ahead of the one-time Context Tree offer, while keeping GitHub App guidance limited to PR tracking.
• Replace the stale GitHub-App/no-repo eval row with a real post-value ad-hoc-repo case and add guards for invitees, already-declared team repos, multi-select misuse, automatic writes, and missing remote inspection.

Why

The welcome flow could use a path or URL for one task but had no explicit bridge from that temporary input to the admin-owned team source-repo setting. The historical post-value confirmation rule had disappeared during the launcher/menu rewrite, while its old eval expectation remained coupled to GitHub App state.

This restores the value-first behavior without putting repo selection back into the onboarding wizard and without giving agents authority to mutate team defaults.

User impact

Admins get one low-friction, post-value confirmation for a repo the agent can identify. Invitees are not sent to admin-only setup, declined repos stay temporary, and existing team sources are not re-confirmed. The resulting team repo remains an explicit admin action in Settings and is available to team agents by default.

Validation

• python3 scripts/quick_validate_skill.py skills/first-tree-welcome
• pnpm --filter @first-tree/skill-evals exec vitest run src/suites/first-tree-welcome/__tests__ — 47 passed
• pnpm --filter @first-tree/skill-evals typecheck
• pnpm --filter @first-tree/skill-evals eval:floor -- --suite first-tree-welcome
• Live periodic eval: first-tree-welcome-ad-hoc-repo-after-value-periodic — passed
• pnpm check — passed with existing repository warnings only
• pnpm typecheck — passed
• pnpm test — welcome/skill-evals passed; one unrelated bundled-Codex capability test timed out under the parallel full suite, then passed in isolation (1 passed, 50 skipped)