Task: write Top-3 and rejection appendix into ROADMAP F3

[Skymly]

Part of #244

Question

After Top-3 is locked: update docs/ROADMAP.md F3 so the candidate pool reflects the admission shortlist and rejection appendix agreed on the map.

Done when: PR/diff (Docs module only) is prepared or merged per maintainer preference; no pattern implementation code.

[Skymly]

Resolution

Updated docs/ROADMAP.md F3 with:

• Top-3: (1) Command Router (2) Builder (3) Fork–Join Work Graph
• Watch list: Resilience Pipeline, Specification, Channel Pipeline, Proxy
• Rejection appendix from Grilling: apply hard gates and draft rejection appendix #251
• Clarified long-term exploration table as existing-domain enhancements (not the new-domain shortlist)

Also noted in CHANGELOG.md [Unreleased] Changed.

Branch: docs/f3-admission-shortlist (local edits; commit/PR pending maintainer).
Map destination for #244 is satisfied once these docs land.

[Skymly]

ROADMAP F3 shortlist written on branch docs/f3-admission-shortlist (ROADMAP + CHANGELOG). Commit/PR pending.