docs(tracker): restructure for readability + complete PR history

[officialCodeWork]

Summary

• Readability: replace the 43K-char header walls (a reverse-chronological prose dump of every step) with a tight Status block, compact per-phase status tables, and per-step detail sections — full detail preserved, lifted out of cramped table cells into bulleted blocks. Longest line dropped 43,654 → 335 chars.
• PR & Branch History rebuilt from GitHub as ground truth: complete through feat(experiments): A/B analyzer + tracker + dashboard (Step 5.7a) #143 (was stale at feat(graphrag): rag-graphrag — community detection + summarisation + graph-aware retrieval (Step 2.9) #96), previously-missing chore(tracker): sync Step 2.5 → ✅ and log PRs #85–#88 #89–chore(tracker): sync Step 2.7 → ✅ and log PR #92 #93 filled in, Dependabot bumps grouped, closed/open PRs marked.
• Stale step status fixed (tracker disagreed with merged code): 5.7a → ✅ (#143), 5.2 → #133, 2.11 → #100.

Content-only doc change — no code, CI, or schemas touched.

Test plan

• All markdown tables validated for column consistency
• No leftover placeholders; header hierarchy clean (## phases / ### steps / #### slices)
• PR links spot-checked against gh pr list
• Render-check the Markdown on GitHub

🤖 Generated with Claude Code