Resolves #14316

Rewrites learn/benefits/AgentOSOnYourCodebase.md into a concrete, source-grounded guide for adopting the Agent OS around a codebase the models were not trained on. The new version explains Knowledge Base, Memory Core, cross-family review, local/cloud deployment, local/remote model routing, self-healing, and the Neural Link boundary without presenting Neural Link as a prerequisite for arbitrary repository learning.

Evidence: L2 (source-grounded guide rewrite + docs lint + browser-backed Mermaid render) -> L2 required for a documentation close target. Residual: none.

Related: #14310

Deltas from ticket

The rewrite keeps the scope to one guide file. learn/tree.json and generated portal SEO artifacts were already current, so this PR does not churn generated files.

The guide explicitly separates repository learning from live runtime possession:

• repository learning: Knowledge Base, Memory Core, Native Edge Graph, tenant ingestion, and review process;
• live Neo UI possession: Neural Link;
• arbitrary runtime possession: future extension, not a current claim.

Test Evidence

• npm run ai:lint-guides — passed; 0 hard failures. The command still reports unrelated existing warnings elsewhere in the docs set.
• npm run ai:lint-tree-json — passed; 212 nodes.
• npm run agent-preflight -- learn/benefits/AgentOSOnYourCodebase.md --pr-body <draft-body> — passed; PR body template anchors present.
• git diff --check — passed.
• Drift sweep against the rewritten guide for client names and disallowed framing terms — passed with no matches.
• Browser-backed Mermaid validation using the installed Mermaid bundle in headless Google Chrome — passed; the extracted TD diagram parsed and rendered to a nontrivial SVG.
• Knowledge Base grounding queries covered Agent OS proof surfaces and whether arbitrary-codebase learning requires Neural Link.
• Memory Core grounding found no strong prior plan for this exact guide rewrite, but did surface older Neural Link context that informed the boundary section.

Post-Merge Validation

• Portal docs page renders the rewritten guide and Mermaid diagram after deployment.

Authored by Euclid (GPT-5, Codex Desktop). Session 4cea162d-b6d0-4f80-9048-ae43a82508de.