docs: strip internal plan/roadmap numbering from user-facing docs

[M0LTE]

Summary

User-facing docs had leftover references to the development plan numbering (F1/F2/F3/F4, B5/B6.1/B6.2, Phase 1/2/2b, Phase H, Phase F3). These codes are meaningful inside `plan.md` but not to a reader of the published manual.

Replaced each with a descriptive name; substantive content unchanged:

• F1 -> "source tracking" / removed where redundant
• F2 -> "multi-part" / "fragmentation"; glossary entry merged into the existing fragment entry
• F3 -> just "rev" / "polling"; glossary entry removed (content already in rev)
• F4 -> versioning policy; glossary entry removed (covered by the DAPPSv1 entry)
• B6.1 -> removed (it's just connected-mode probing)
• B6.2 -> removed (it's just solicit-and-listen)
• Phase 1 / Phase 2 / Phase 2b probe flavours -> direct / transitive / node-prompt
• Phase H links to plan.md -> "on the roadmap" with link to `connect/meshcore.md`

8 files touched, 29 insertions, 37 deletions.

Test plan

• `grep -rE '\bF[1-4]\b|\bB[5-7]\b|Phase [A-Z0-9]|Plan [A-Z0-9]'` clean across published docs (excluding the engineering-note files `routing-prior-art.md` and `meshcore-backhaul-routing.md` which are already excluded from the mkdocs site)
• `mkdocs build --strict` clean
• No file:line citations broken (`implement.md` still cites canonical source files)
• Glossary entries that were removed have their content covered by other entries (`fragment`, `rev`, `DAPPSv1`)

🤖 Generated with Claude Code