docs: clarify Daedalus-Pallas integration auth model

Refine the phase-2 integration spec to reflect implementation details:

- Change `resolved_libraries` from `set[str]` to ordered `list[str]`
- Document `MCPToken.allowed_libraries` as JSONField (not M2M) since
  Library lives in Neo4j, not Django's ORM
- Clarify that `Library.workspace_id` is a content-routing attribute,
  not an authorization axis
- Describe retirement of the three-branch `_WORKSPACE_SCOPE_CLAUSE` in
  favor of a single `lib.uid IN $resolved_libraries` check
- Specify team JWT resolution via `TeamWorkspaceAssignment` DB join
- Note admin UI materializes full Library UID list explicitly

mnemosyne/mcp_server/context.py

@@ -1,10 +1,35 @@
-"""Helpers for accessing the request-scoped MCP user/token from inside tools."""
+"""Helpers for accessing the request-scoped MCP auth state from inside tools.
+
+The authoritative values are set by :class:`mcp_server.auth.MCPAuthMiddleware`
+on the FastMCP ``Context``:
+
+* ``STATE_KEY_USER`` — the Django user the bearer resolved to (synthetic
+  service user for JWT callers, concrete ``mcp_tokens.user`` for opaque
+  MCPToken callers, ``None`` for team JWTs which are not tied to any
+  per-user account).
+* ``STATE_KEY_TOKEN`` — the ``MCPToken`` row for opaque-token callers;
+  ``None`` for JWT callers.
+* ``STATE_KEY_CLAIMS`` — the JWT claims dict for JWT callers; ``None``
+  for opaque-token callers. Intentionally exposed for debugging /
+  metrics; tools should NOT branch on claim shape for authorization,
+  they should read :func:`get_mcp_resolved_libraries` instead.
+* ``STATE_KEY_RESOLVED_LIBRARIES`` — the authorization-resolved Library
+  UID set for this request. ``None`` means the caller is unauthenticated
+  or the auth middleware was bypassed (shouldn't happen in practice);
+  ``[]`` means the caller is authenticated but scoped to zero libraries
+  (fail-closed); a non-empty list enumerates the UIDs the caller may read.
+"""
 
 from __future__ import annotations
 
 from fastmcp.server.context import Context
 
-from .auth import STATE_KEY_CLAIMS, STATE_KEY_TOKEN, STATE_KEY_USER
+from .auth import (
+    STATE_KEY_CLAIMS,
+    STATE_KEY_RESOLVED_LIBRARIES,
+    STATE_KEY_TOKEN,
+    STATE_KEY_USER,
+)
 
 
 async def get_mcp_user(ctx: Context | None):
@@ -24,3 +49,23 @@ async def get_mcp_claims(ctx: Context | None) -> dict | None:
     if ctx is None:
         return None
     return await ctx.get_state(STATE_KEY_CLAIMS)
+
+
+async def get_mcp_resolved_libraries(ctx: Context | None) -> list[str] | None:
+    """Return the authorization-resolved Library UID list for this request.
+
+    Semantics (matching ``SearchRequest.resolved_libraries``):
+
+    * ``None`` — no auth information available (e.g. the middleware did
+      not run, or the tool was invoked outside a request context). Tools
+      should treat this as fail-closed and refuse to return content.
+    * ``[]`` — the caller was authenticated but is scoped to zero
+      libraries. Tools MAY proceed and return empty results.
+    * ``["lib_x", …]`` — the caller may read exactly these libraries.
+
+    See ``docs/DAEDALUS_PALLAS_INTEGRATION_v1.md`` §3.3 for the unified
+    auth model that populates this value.
+    """
+    if ctx is None:
+        return None
+    return await ctx.get_state(STATE_KEY_RESOLVED_LIBRARIES)