Roadmap rewrite: dashboard-first release tracks plus dashboard spec

[SethGammon]

What changed

• docs/ROADMAP.md rewritten around five release tracks: See It (local dashboard over .planning state), Prove It (public reproducible benchmarks), Drive It (two-way operator surface via intent files), Harden It (teams-native fleet GA plus security v2), Multiply It (team workflows, skill and loop registry, third runtime adapter).
• Shipped milestones (M0, M1, M2 core, M5) recorded as foundations; unshipped M3/M4/M6/M7 items absorbed into the tracks rather than dropped. Hosted relay explicitly parked with no scheduled date and a rule that nothing may depend on a hosted service.
• New docs/DASHBOARD_SPEC.md for R1 v0.1: read-only architecture (Node server, SSE invalidation, files canonical), per-source data contracts, the needs-you inbox, dual-mode cost (estimated USD for API-key users, plan-window burn for subscribers, local OTLP receiver consuming claude_code.cost.usage and claude_code.token.usage with transcript and Codex fallbacks), six panels, performance budgets, and the verification plan.
• README roadmap section synced to the new tracks.

Verification

npm test passes (full suite including doc-surface checks).