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>

tests/test_budget_registry.py

@@ -522,7 +522,7 @@ def test_emit_token_event_calls_poster_with_record_token_payload(tmp_path: Path)
     assert result["status"] == "emitted"
     assert len(calls) == 1
     url, payload, timeout = calls[0]
-    assert url == "http://hub.example/state/token-events"
+    assert url == "http://hub.example/token-events/"
     assert payload["tokens_in"] == 1200
     assert payload["tokens_out"] == 400
     assert payload["model"] == "openai/gpt-4o-mini"