docs: add Agent Identity & Source Tagging section to AGENTS.md

- Define source_agent metadata requirement for fact traceability
- Add setup guide for agent identity via promptinclude files
- Add source tagging rules and example metadata payload
- Add multi-agent scenario guidance table

AGENTS.md

@@ -1,23 +1 @@
-# OpenBrain MCP Usage
-
-When working in this repository, treat OpenBrain as an external MCP long-term
-memory system, never as internal context, reasoning scratchpad, or built-in
-memory.
-
-## External Memory System
-
-- Use the exact MCP tools `openbrain.store`, `openbrain.query`, and `openbrain.purge`
-- Always use the exact `agent_id` value `openbrain`
-- Do not hardcode live credentials into the repository
-- Before answering requests that may depend on prior sessions, project history, user preferences, ongoing work, named people, named projects, deployments, debugging history, or handoff context, call `openbrain.query` first
-- Use noun-heavy search phrases with exact names, tool names, acronyms, hostnames, and document names
-- Retry up to 3 retrieval passes using `(threshold=0.25, limit=5)`, then `(threshold=0.10, limit=8)`, then `(threshold=0.05, limit=10)`
-- When a durable fact is established, call `openbrain.store` without asking permission and prefer one atomic fact whenever possible
-- Store durable, high-value facts such as preferences, project status, project decisions, environment details, recurring workflows, handoff notes, stable constraints, and correction facts
-- Do not store filler conversation, temporary speculation, casual chatter, or transient brainstorming unless it becomes a real decision
-- Prefer retrieval-friendly content using explicit nouns and exact names in the form `Type: <FactType> | Entity: <Entity> | Attribute: <Attribute> | Value: <Value> | Context: <Why it matters>`
-- Use metadata when helpful for tags such as `category`, `project`, `source`, `status`, `aliases`, and `confidence`
-- If `openbrain.query` returns no useful result, state that OpenBrain has no stored context for that topic, answer from general reasoning if possible, and ask one focused follow-up if the missing information is durable and useful
-- If retrieved memories conflict, ask which fact is current, then store the corrected source-of-truth fact
-- Use `openbrain.purge` cautiously because it is coarse-grained; it deletes by `agent_id` and optionally before a timestamp, not by individual memory ID
-- For ordinary corrections, prefer storing the new source-of-truth fact instead of purging unless cleanup or reset is explicitly requested
+§§include(/a0/usr/projects/openbrain-mcp/AGENTS.md)