Add agent_id field to SessionSource and SessionEntry, prefix session keys
with agent:<id>: in build_session_key. Default "main" preserves every
historical key string for single-agent installs.

- gateway/session.py: SessionSource.agent_id, SessionEntry.agent_id,
  build_session_key prefixing
- hermes_state.py: sessions table migration (agent_id TEXT DEFAULT 'main'),
  new idx_sessions_agent index
- tests/gateway/test_session.py: build_session_key prefixing for all
  chat_type × agent_id combinations
- tests/*/test_session_boundary_hooks.py: hook payload agent_id kwarg

… hook

Add declarative routing (routes: match → agent) and a select_agent plugin
hook. _attach_agent_id injects the resolved agent_id into event.source
before build_session_key. Seven platform adapters get pre-injection for
batching paths; the rest inherit it from base.py.

- gateway/agent_routing.py: resolve_agent_id(), _route_matches()
- gateway/config.py: agents, routes, default_agent schema
- gateway/platforms/base.py: _attach_agent_id(), set_routing_context()
- gateway/platforms/{telegram,discord,slack,matrix,feishu,wecom,yuanbao}.py:
  pre-batch injection
- hermes_cli/plugins.py: select_agent hook registration
- tests/gateway/test_agent_routing.py: declared-order matching, hook chain,
  default fallback, profile isolation

…s agent_id to hooks

GatewayRunner loads the agent registry at init and wraps every inbound
message in use_profile(). AIAgent accepts an optional profile= kwarg.
All invoke_hook call sites gain agent_id= kwarg. _handle_message is
split into _handle_message (ContextVar plumbing) + _handle_message_inner
(legacy logic) so tests that grep the source body continue to work.

- gateway/run.py: registry loading, use_profile() wrapping, hook kwargs
- run_agent.py: AIAgent(profile=), profile-aware model/toolset resolution
- model_tools.py, tools/{approval,terminal,delegate}.py: hook agent_id
- cli.py, tui_gateway/server.py: session boundary hook agent_id
- tests/gateway/test_profile_overrides.py: per-agent model/toolset overrides
- tests/test_model_tools.py: hook payload verification
- tests/gateway/test_{update,title,reasoning}_command.py: adapt to
  _handle_message split

The MGA series added _attach_agent_id() into the handle_message hot path
(base.py:handle_message). It reads three instance attributes set only in
BasePlatformAdapter.__init__: _default_agent_id, _gateway_routes, and
_gateway_ref. Any adapter constructed without running __init__ (or a
future partial-construction path) crashes with AttributeError on
_default_agent_id, which is read outside the existing try/except.

Because this runs on every inbound message, a missing attribute would
crash real message processing, not just tests. Harden the method to read
all three via getattr() with safe defaults so a partially-constructed
adapter degrades to the "main" agent instead of raising.

Also fix the _make_adapter() test helper, which deliberately bypasses
__init__ via object.__new__() and hand-sets attributes: it predated the
MGA routing attributes and never set them. Add the three so the mock
faithfully mirrors a real __init__-constructed adapter.

Fixes 10 regressions in tests/gateway/test_active_session_text_merge.py.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Empty commit to fire push event so the fix(gateway) delivery.py
commit (6fbb441) is picked up by NousResearch CI.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>