docs(benefits): nested-folder tree structure + reading-order WEIGHTING (Start-Here / Brain / Body)

Part of #14310. Refs #14310.

Problem: learn/benefits/ is 19 flat files with no reading order — Body + Brain benefits jumbled. The single biggest comprehension lever is structure + WEIGHTING: how the tree is organized and what to read in which order, easy to follow. The portal Learning section already renders nested folders / the tree.json structure out of the box (with prev/next) — so this is purely a content-tree + ordering task, no portal code (verified: learn/tree.json is the consumed nav SSOT — SEO generation + the portal read it).

The target weighted tree (the deliverable)

Weighted by genuinely-unique-and-ahead (⭐ = nobody else has it), matching the v13.0.0 hero hierarchy — crown jewels lead, enabling substrate drops below the wow.

📍 Start Here
   1. What Is Neo?  (#14313 — the organism + why)
   2. Architecture Overview  (#14315 — two hemispheres + main-areas map; threads the
                              object-permanence-of-identity Body↔Brain symmetry)

🧠 The Brain — the self-evolving AI institution        ← lead with the wow
   3. The AI Engineering Team            (#14320)
   4. ⭐ The Night Shift — autonomous mode (#14331 — runs while you sleep · 10–20 PRs · cross-family quorum)
   5. ⭐ The Golden Path — forecasts the next move (#14318/#14320 — sandman_handoff.md)
   6. Agent Memory & the Native Edge Graph (#14317/#14321 — memory→telepathy · 19k nodes · active GraphRAG)
   7. ⭐ Identity, Rituals & Culture       (#14332 — same model ≠ same agent; object permanence for the Brain;
                                            sunset-handover ≠ sandman_handoff)
   8. Self-Healing — the immune system    (#14322 — runs unattended)
   9. The Agent OS on Your Codebase       (#14316)   →   10. Deploying the Agent OS (#14321/#14324 → cloud path)

🔧 How the institution runs  (enabling substrate — reachable, below the wow)
   · A2A messaging (#14328) · Wakes & hooks / mechanical enforcement (#14329)
   · The core agent skills (#14330) · Model providers: local vs remote (#14323)
   · Coordination bigger-picture (#14331)   · + whatever #14333 (ai/-folder audit) surfaces

🤖 The Body — Application Engine
   Application Engine (#14311 renamed) · Object Permanence (cross-link → Identity #14332) · JSON-First UIs ·
   Off-Main-Thread · Multi-Window · Speed · Forms · Config System · RPC Layer · 4 Environments · Quick Dev ·
   Effort · Features Summary

Acceptance Criteria

• Reorganize learn/benefits/ into nested folders the portal renders out-of-the-box — start-here/, brain/, body/ — populated + ordered per the target tree above (the ⭐ crown jewels lead the Brain group).
• learn/tree.json reflects the nested structure + the exact reading order (what to read first → last); no broken ids; hidden/collapsed sane; inbound links to moved docs updated.
• Weighting is the deliverable, not just grouping — the order tells the story (what is Neo → the institution's unique wow → how it runs → the runtime).
• Coordinates with #14311 (rename → Body), #14313 (new intro = Start-Here #1), #14332 (Identity = Brain crown jewel).

⚠️ V-B-A grounding (mandatory): learn/tree.json (the SSOT) + how apps/portal renders it (confirm folder-driven vs tree.json-driven; SEO gen at buildScripts/docs/seo/generate.mjs consumes it) + the full learn/benefits/ inventory. Driver: @neo-opus-grace.

Note: absorbs the (closed) #14314 — the portal already renders the nested tree + prev/next; the work is the tree structure + weighting it renders.