Extract duplicated bus/provider/loop initialization from CLI commands
(serve, _run_gateway, agent) and Nanobot facade into a single
AgentLoop.from_config() classmethod.
- Remove _make_provider() from cli/commands.py and nanobot.py
- Remove inline provider creation in all three CLI entry points
- AgentLoop.from_config() creates MessageBus, calls make_provider(),
and assembles AgentLoop with all standard config-derived parameters
- Supports **extra overrides for callers that need custom args
(e.g. cron_service, session_manager, provider_snapshot_loader)
- Update tests to mock make_provider at nanobot.providers.factory
and add from_config classmethod to _FakeAgentLoop fixtures
This is PR 1/4 of the model-preset feature decomposition.
``Nanobot.run()`` has always documented ``RunResult.tools_used`` and
``RunResult.messages`` but actually returned ``[]`` for both, so SDK
consumers could never inspect which tools fired or what the final
message list looked like — the only useful field was ``content``.
This threads the data out via a tiny ``_SDKCaptureHook`` that installs
alongside any user-supplied hooks. The capture hook accumulates tool
names across iterations and snapshots the message list on each
``after_iteration`` call; the last snapshot reflects end-of-turn state.
Only the SDK facade is touched: ``AgentLoop.process_direct`` and
``AgentRunner`` signatures are unchanged, so channels / CLI / API paths
are unaffected.