Add a public-safe sample board pack for Settings → Import demos

[telivity-otaip]

Why

Newcomers who self-host land on an empty board. A fictional board pack they can import from Settings makes the product clickable in under a minute — and gives docs/tests a stable fixture.

Size

S — one JSON fixture + short docs note.

Task

1. Add something like docs/fixtures/sample-board-pack.json (or scripts/fixtures/) that:
   • uses fake companies only (Acme, Northwind, Contoso…)
   • includes a few roles across stages, 1–2 fake accomplishments, optional interview event / contact
   • validates against current pack format (schema_version 5, format careerops-board-pack/v5)
   • contains no API keys, emails of real people, or identifiable employers
2. Document in web/README.md (Export/import) or docs/BOARD_PACK.md: “Import this sample from Settings → Your data.”
3. Optional: assert the fixture round-trips in scripts/test-career-os.mjs (import plan does not throw).

Acceptance

• Fixture imports cleanly into a fresh self-host (or passes the pack reader/migrator in tests)
• Clearly labeled SEEDED / FICTIONAL in the file or docs
• No PII, no real job pipeline data
• Keys/secrets absent

Tips

Study buildBoardPack output shape in web/lib/board-pack.mjs. Demo asset doctrine lives in docs/assets/README.md — same privacy bar.