Named custom providers are rewritten to provider="custom" at runtime
(hermes_cli/runtime_provider.py:_resolve_named_custom_runtime), so a
config under providers.my-vllm.models.my-llava.supports_vision was
unreachable via self.provider alone. Also try cfg.model.provider as a
candidate provider key, covering both runtime and config naming.

Adds a regression test for the named-provider path.

The contributor PR (#17936) only patched the strip path in
`_model_supports_vision()`. The auto-mode router in
`agent/image_routing._lookup_supports_vision` still only read models.dev,
so a custom-provider model declared as vision-capable would still get its
images routed through vision_analyze in the default `agent.image_input_mode:
auto` setting. Users had to set both `supports_vision: true` AND
`image_input_mode: native` to bypass the text pipeline.

Single-knob behavior now: `supports_vision: true` alone is enough in auto
mode. The strip path and the routing path consult the same resolver.

- Extract override resolution into `_supports_vision_override()` in
  agent/image_routing.py and wire it into `_lookup_supports_vision()`.
- Refactor `run_agent._model_supports_vision` to call the same helper
  (DRY, single source of truth for the resolution order).
- Strict YAML boolean coercion: `supports_vision: "false"` (quoted —
  a common YAML mistake) no longer coerces to True via bool() truthiness.
  Recognised tokens: true/false/yes/no/on/off/1/0 plus real bools and 0/1.
  Unrecognised values return None and fall through to models.dev.
- Add @CNSeniorious000 to AUTHOR_MAP for release attribution.

Tests: 26 new (TestCoerceCapabilityBool, TestSupportsVisionOverride,
TestLookupSupportsVisionOverride, TestAutoModeRespectsOverride). Existing
contributor tests + image_routing + vision_native_fast_path +
native_image_buffer_isolation all green (92/92).

The interactive CLI input path consults decide_image_input_mode() to pick
between native image_url attachment and the vision_analyze text pipeline,
but the non-interactive 'hermes chat -Q -q ... --image FOO' path
unconditionally called _preprocess_images_with_vision() — so even with
`model.supports_vision: true` set, --image always went through the
text-pipeline. Symptom: vision_analyze runs 4-5s per image and the model
sees a lossy text summary instead of the actual pixels.

Mirror the interactive path: load config, call decide_image_input_mode,
branch on native vs text. Falls back to the text-pipeline on any import
or build error (Pyright-clean: _build_parts guarded with `is not None`).

Live E2E (provider=custom, base_url=openrouter, anthropic/claude-haiku-4.5,
red 64x64 PNG):
  baseline (no override): vision_analyze called (8 log lines), 5.8s
  with supports_vision:   vision_analyze NOT called (0 log lines),  3.9s
Same model, same image, single knob flips text→native routing.