Update ROADMAP.md on Phase 2 completion

[TFT444]

Overview

Once all Phase 2 issues are merged and CI is green on main, update ROADMAP.md to mark Phase 2 complete and set Phase 3 as "In Development".

Changes

• Mark all Phase 2 checkboxes [x]
• Update rule count throughout (20 → 26)
• Add ## Phase 2 — Complete (v2.1.0, Q3 2026) header
• Move Phase 3 section header to ## Phase 3 — In Development (v3.0.0, 2027)
• Update *Last updated* date

Acceptance criteria

• All Phase 2 items checked off
• Rule count consistent throughout the file
• Phase 3 marked "In Development"
• Date updated

Blocked until

All of: #119, #120, #121, #122, #123, #124, #125, #126, #127, #128, #129, #130, #131, #132, #133, #134 are merged