feat: multi-agent architecture — named agents with routing, tool policies, and isolated workspaces

Implements the full multi-agent system for Hermes Agent, allowing a single
installation to host multiple named agents, each with its own model,
personality, toolset, workspace, and session history.

## New Files

- gateway/agent_registry.py: AgentConfig, ToolPolicy, SubagentPolicy,
  AgentRegistry, TOOL_PROFILES (minimal/coding/messaging/full), and
  normalize_tool_config() for shorthand YAML parsing

- gateway/router.py: BindingRouter with 7-tier deterministic routing
  (chat_id > peer > guild+type > guild > platform+type > platform > default)

## Core Changes

- model_tools.py: get_tool_definitions() accepts agent_tool_policy for
  per-agent tool filtering; handle_function_call() extended enabled_tools
  check to gate ALL tool calls (defense-in-depth)

- gateway/session.py: build_session_key() now accepts agent_id and dm_scope
  parameters, replacing hardcoded 'agent:main' with 'agent:{agent_id}'

- tools/memory_tool.py: MemoryStore accepts memory_dir parameter for
  per-agent memory isolation

- agent/prompt_builder.py: build_context_files_prompt() accepts
  agent_workspace for SOUL.md lookup; build_skills_system_prompt()
  accepts agent_skills_dir for per-agent skill overlay

- run_agent.py: AIAgent accepts agent_tool_policy and agent_workspace,
  passes policy through to get_tool_definitions()

- gateway/run.py: Initializes AgentRegistry + BindingRouter, resolves
  agent per-message in _handle_message(), passes config to _run_agent(),
  adds /agents command

- cli.py: --agent flag for selecting named agent profiles, /agents
  slash command, agent config override for model/personality/tools

- hermes_cli/config.py: agents/bindings in DEFAULT_CONFIG, version 7

- tools/delegate_tool.py: Configurable max_depth per-agent, tool policy
  inheritance from parent to child

## Config Format

agents:
  main:
    default: true
  coder:
    model: anthropic/claude-sonnet-4
    personality: 'You are a coding assistant.'
    tools: coding  # or [tool1, tool2] or {profile: x, deny: [...]}

bindings:
  - agent: coder
    telegram: '-100123456'

## Tests

168 new tests across 3 test files (agent_registry, router, integration).
All 3106 tests pass.

hermes_cli/config.py

@@ -126,6 +126,14 @@ DEFAULT_CONFIG = {
         # "model": "google/gemini-3-flash-preview",
     },
 
+    # Named agent profiles — reusable bundles of model + toolsets + prompt.
+    # Define profiles here and activate them with `hermes chat --agent <name>`.
+    "agents": {},
+
+    # Bindings — map trigger patterns or platforms to named agent profiles.
+    # Example: [{"pattern": "review *", "agent": "code-reviewer"}]
+    "bindings": [],
+
     "display": {
         "compact": False,
         "personality": "kawaii",
@@ -189,7 +197,7 @@ DEFAULT_CONFIG = {
     "command_allowlist": [],
 
     # Config schema version - bump this when adding new required fields
-    "_config_version": 6,
+    "_config_version": 7,
 }
 
 # =============================================================================
@@ -654,6 +662,23 @@ def migrate_config(interactive: bool = True, quiet: bool = False) -> Dict[str, A
                 tz_display = config["timezone"] or "(server-local)"
                 print(f"  ✓ Added timezone to config.yaml: {tz_display}")
 
+    # ── Version 6 → 7: add agents and bindings keys ──
+    if current_ver < 7:
+        config = load_config()
+        changed = False
+        if "agents" not in config:
+            config["agents"] = {}
+            results["config_added"].append("agents={}")
+            changed = True
+        if "bindings" not in config:
+            config["bindings"] = []
+            results["config_added"].append("bindings=[]")
+            changed = True
+        if changed:
+            save_config(config)
+            if not quiet:
+                print("  ✓ Added agents and bindings to config.yaml")
+
     if current_ver < latest_ver and not quiet:
         print(f"Config version: {current_ver} → {latest_ver}")