docs: concept annexation, provider/reference docs, ACT-1 groundwork

Mosaic concepts pages now own the adapted content; source/license
metadata under docs/reference/concepts. Adds ACT-1 agent-context
planning capture, pinned concept test package + preparation utility,
foundation observation notes (durability, evidence, federation,
onboarding, workflow), and the #1495 consolidation assessment.
TOOLS.md updated for the host-dev launcher.

docs/reference/templates/USER.md

@@ -0,0 +1,36 @@
+---
+summary: "Durable user preference and profile directives"
+title: "USER template"
+read_when:
+  - Bootstrapping a workspace manually
+---
+
+# USER.md - User Model
+
+Store stable user preferences and profile facts as directives that can guide future sessions.
+
+Use one directive per entry:
+
+```md
+<!-- observed: YYYY-MM-DD | status: active -->
+
+- Prefer concise progress updates during implementation work.
+```
+
+- Begin each directive with an imperative such as `Always`, `Never`, or `Prefer`.
+- Record the observation date and either `active` or `superseded` on the metadata line.
+- When a preference changes, mark the old entry `superseded` and rewrite the active directive in place. Never append a contradictory active directive.
+- Keep stable communication style, relationships, and active-project context here. Put durable non-profile facts and decisions in `MEMORY.md`.
+- Save this file at the workspace root as `USER.md`. It loads every session with a separate 4,000-character budget.
+
+## Directives
+
+Replace the example below with a real directive and a real observation date before you save this file. Never leave a placeholder directive `active`.
+
+<!-- observed: YYYY-MM-DD | status: active -->
+
+- Prefer ...
+
+## Related
+
+- [Agent workspace](/concepts/agent-workspace)