Sync docs/SPEC.md Phase 1 checklist after issue #3 merged #22

What

Why (motivation)

PR #10 (commit a53e72f) shipped the mobile Linear ticket client and closed issue #3, but the Phase 1 roadmap checkbox in docs/SPEC.md was never flipped to reflect it

User impact

Contributors and agents reading docs/SPEC.md (the authoritative spec per repo CLAUDE.md) see a stale checklist claiming Linear client work is still outstanding, risking duplicate or mis-scoped work

Cost of inaction

docs/SPEC.md keeps understating delivered scope indefinitely, eroding its authority as the single source of truth

Acceptance criteria

• docs/SPEC.md Phase 1 checklist shows the 'Linear client (tickets)' line checked ([x])
• No other checklist lines change

Screenshots

(none)

Links

• (none)

Skipped gates

• links: title is plain text (no markdown links supported there) and contains 'docs/SPEC.md' + 'Mobile: Linear client (tickets, offline view) #3' as bare identifiers by necessity; both are fully linked in the why/impact/if-not-done body fields above