IB-WP-0020-T03: routing CLI flags

Add --provider routing, --routing-config <yaml>, and --quality-floor
<float> to generate run, generate resume, and generate from-source.
The CLI flag wiring constructs a RoutingAssistedGenerationAdapter from
the parsed config, with the workspace handed in so any ledger_path in
the config resolves relative to it. --quality-floor overrides the
config-level default_quality_floor for a single invocation.

run_generation gains routing_config + quality_floor kwargs and
_adapter_for grew a "routing" branch. Missing --routing-config with
--provider routing fails fast with InfospaceError("missing_routing_config");
missing API key for any candidate fails fast with
InfospaceError("missing_routing_api_key").

Two small bug fixes surfaced while writing T03:

- routing._identify_adapter now also reads ``_model`` from llm-connect
  adapters (their public attribute is private), so the per-stage
  adapter-choice line shows the model id rather than just the class
  name.
- budget.TOKEN_EVENTS_PATH corrected from /state/token-events to the
  state-hub HTTP endpoint /token-events/ that actually exists; the
  failure-isolation in emit_token_event already kept the prior typo
  from breaking runs, but the hub never saw the events.

Five new tests cover: _adapter_for refusal on missing config,
_adapter_for happy path, run_generation end-to-end through routing
with a stubbed OpenRouterAdapter.execute_prompt (no network),
workspace-relative ledger resolution, and a CLI subprocess smoke
asserting fast-fail on missing API key.

173 tests pass, 1 skipped.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workplans/IB-WP-0020-provider-routing-cli.md

@@ -117,7 +117,7 @@ state_hub_task_id: "5e38514b-ad6a-4d39-8716-f812f241d9fd"
 
 ```task
 id: IB-WP-0020-T03
-status: todo
+status: done
 priority: high
 state_hub_task_id: "fe5888e0-da33-413a-b026-71ed811b8c73"
 ```