refactor: collapse strix/io/, strix/run_config_factory.py, strix/entry.py

Three top-level files that didn't earn their place:

- ``strix/io/scan_artifacts.py`` had a single consumer (the Tracer);
  collapsing it into ``strix/telemetry/`` puts it next to that consumer.
  ``strix/io/`` is gone.

- ``strix/run_config_factory.py`` held two helpers that didn't earn the
  factoring. ``make_agent_context`` was a 17-line dict-spelling function
  whose argument names were identical to its dict keys — replaced with
  inline dict literals at the two call sites. ``make_run_config`` had
  enough RunConfig assembly logic to justify a helper, but with only
  two callers (root scan + ``create_agent``) inlining is cleaner than
  keeping a top-level file. ``DEFAULT_RETRY`` moves to
  ``strix/llm/retry.py`` next to its other LLM-policy peers; the dead
  ``STRIX_DEFAULT_MAX_TURNS`` constant is dropped.

- ``strix/entry.py`` is a misnomer — it isn't *the* entry point (that's
  ``strix/interface/main.py`` for the CLI), it's the per-scan bring-up
  driver: build the bus, bring up the sandbox, build the root agent +
  child factory, format the scope-context block, register root in bus,
  open SQLiteSession, hand off to ``run_with_continuation``. That all
  lives next to its peers in ``strix/orchestration/`` now, renamed to
  ``scan.py`` so the role is obvious.

No behavior change. Net -125 LoC.

strix/interface/cli.py

@@ -14,7 +14,7 @@ from rich.panel import Panel
 from rich.text import Text
 
 from strix.config import load_settings
-from strix.entry import run_strix_scan
+from strix.orchestration.scan import run_strix_scan
 from strix.runtime import session_manager
 from strix.telemetry.tracer import Tracer, set_global_tracer