What happened?
The get_page MCP tool ignores the per-call source_id parameter. MCP clients with a default-source bearer (e.g. hermes-write configured with source_id=default) cannot get_page pages in non-default sources — they get page_not_found, even when the page exists in the DB and the bearer has federated_read access.

The query tool already supports per-call source_id (via --source-id flag, v0.34). get_page should mirror that behavior.

What did you expect?
get_page({slug: "X", source_id: "priv-foo"}) returns the page when source priv-foo is in the bearer's federated_read list, regardless of ctx.sourceId.

Steps to reproduce

1. Create a page in a non-default source:
   docker exec gbrain-postgres psql -U gbrain -d gbrain -c
   "INSERT INTO pages (slug, source_id, body) VALUES ('test/page', 'priv-test', 'body');"
2. Use a bearer with source_id=default AND priv-test in federated_read.
3. Call get_page:
   curl -X POST http://localhost:3131/mcp
   -H "Authorization: Bearer "
   -H "Content-Type: application/json"
   -H "Accept: application/json, text/event-stream"
   -d '{"jsonrpc":"2.0","id":1,"method":"tools/call",
   "params":{"name":"get_page",
   "arguments":{"slug":"test/page","source_id":"priv-test"}}}'
   Returns: {"error":"page_not_found"} — even though the page exists.
4. query with same source_id works correctly — finds the page

Environment

• gbrain version: 0.35.0.0
• OS: macOS
• Bun version: 1.3.14
• Database: self-hosted Postgres (Docker, pgvector/pgvector:pg16)

gbrain doctor --json output

{
    "schema_version": 2,
    "status": "ok",
    "health_score": 95,
    "checks": [
      {"name": "connection", "status": "ok", "message": "Connected, 2210 pages"},
      {"name": "pgvector", "status": "ok", "message": "Extension installed"},
      {"name": "rls", "status": "ok", "message": "RLS enabled on 42/42 public tables"},
      {"name": "schema_version", "status": "ok", "message": "Version 66 (latest: 66)"},
      {"name": "embedding_provider", "status": "ok", "message": "ollama:nomic-embed-text"},
      {"name": "search_mode", "status": "ok", "message": "Mode: tokenmax"},
      {"name": "reranker_health", "status": "ok", "message": "zeroentropyai:zerank-2 reachable"}
    ],
    "note": "Output truncated — only fields relevant to MCP get_page bug. Full doctor output available on request."
  }