feat: provider modules — ProviderProfile ABC, 33 providers, fetch_models, transport single-path

Introduces providers/ package — single source of truth for every
inference provider. Adding a simple api-key provider now requires one
providers/<name>.py file with zero edits anywhere else.

What this PR ships:
- providers/ package (ProviderProfile ABC + 33 profiles across 4 api_modes)
- ProviderProfile declarative fields: name, api_mode, aliases, display_name,
  env_vars, base_url, models_url, auth_type, fallback_models, hostname,
  default_headers, fixed_temperature, default_max_tokens, default_aux_model
- 4 overridable hooks: prepare_messages, build_extra_body,
  build_api_kwargs_extras, fetch_models
- chat_completions.build_kwargs: profile path via _build_kwargs_from_profile,
  legacy flag path retained for lmstudio/tencent-tokenhub (which have
  session-aware reasoning probing that doesn't map cleanly to hooks yet)
- run_agent.py: profile path for all registered providers; legacy path
  variable scoping fixed (all flags defined before branching)
- Auto-wires: auth.PROVIDER_REGISTRY, models.CANONICAL_PROVIDERS,
  doctor health checks, config.OPTIONAL_ENV_VARS, model_metadata._URL_TO_PROVIDER
- GeminiProfile: thinking_config translation (native + openai-compat nested)
- New tests/providers/ (79 tests covering profile declarations, transport
  parity, hook overrides, e2e kwargs assembly)

Deltas vs original PR (salvaged onto current main):
- Added profiles: alibaba-coding-plan, azure-foundry, minimax-oauth
  (were added to main since original PR)
- Skipped profiles: lmstudio, tencent-tokenhub stay on legacy path (their
  reasoning_effort probing has no clean hook equivalent yet)
- Removed lmstudio alias from custom profile (it's a separate provider now)
- Skipped openrouter/custom from PROVIDER_REGISTRY auto-extension
  (resolve_provider special-cases them; adding breaks runtime resolution)
- runtime_provider: profile.api_mode only as fallback when URL detection
  finds nothing (was breaking minimax /v1 override)
- Preserved main's legacy-path improvements: deepseek reasoning_content
  preserve, gemini Gemma skip, OpenRouter response caching, Anthropic 1M
  beta recovery, etc.
- Kept agent/copilot_acp_client.py in place (rejected PR's relocation —
  main has 7 fixes landed since; relocation would revert them)
- _API_KEY_PROVIDER_AUX_MODELS alias kept for backward compat with existing
  test imports

Co-authored-by: kshitijk4poor <82637225+kshitijk4poor@users.noreply.github.com>
Closes #14418

hermes_cli/models.py

@@ -806,6 +806,25 @@ CANONICAL_PROVIDERS: list[ProviderEntry] = [
     ProviderEntry("ai-gateway",     "Vercel AI Gateway",        "Vercel AI Gateway"),
 ]
 
+# Auto-extend CANONICAL_PROVIDERS with any provider registered in providers/
+# that is not already in the list above.  Adding providers/*.py is sufficient
+# to expose a new provider in the model picker, /model, and all downstream
+# consumers — no edits to this file needed.
+_canonical_slugs = {p.slug for p in CANONICAL_PROVIDERS}
+try:
+    from providers import list_providers as _list_providers_for_canonical
+    for _pp in _list_providers_for_canonical():
+        if _pp.name in _canonical_slugs:
+            continue
+        if _pp.auth_type in ("oauth_device_code", "oauth_external", "external_process", "aws_sdk", "copilot"):
+            continue  # non-api-key flows need bespoke picker UX; skip auto-inject
+        _label = _pp.display_name or _pp.name
+        _desc = _pp.description or f"{_label} (direct API)"
+        CANONICAL_PROVIDERS.append(ProviderEntry(_pp.name, _label, _desc))
+        _canonical_slugs.add(_pp.name)
+except Exception:
+    pass
+
 # Derived dicts — used throughout the codebase
 _PROVIDER_LABELS = {p.slug: p.label for p in CANONICAL_PROVIDERS}
 _PROVIDER_LABELS["custom"] = "Custom endpoint"  # special case: not a named provider
@@ -2023,6 +2042,34 @@ def provider_model_ids(provider: Optional[str], *, force_refresh: bool = False)
                 return ids
         except Exception:
             pass
+
+    # ── Profile-based generic live fetch (all simple api-key providers) ──
+    # Handles any provider registered in providers/ with auth_type="api_key".
+    # Replaces per-provider copy-paste blocks (stepfun, gmi, zai, etc.).
+    try:
+        from providers import get_provider_profile
+        from hermes_cli.auth import resolve_api_key_provider_credentials
+
+        _p = get_provider_profile(normalized)
+        if _p and _p.auth_type == "api_key" and _p.base_url:
+            try:
+                creds = resolve_api_key_provider_credentials(normalized)
+                api_key = str(creds.get("api_key") or "").strip()
+                base_url = str(creds.get("base_url") or "").strip()
+            except Exception:
+                api_key, base_url = "", _p.base_url
+            if not base_url:
+                base_url = _p.base_url
+            if api_key:
+                live = _p.fetch_models(api_key=api_key)
+                if live:
+                    return live
+            # Use profile's fallback_models if defined
+            if _p.fallback_models:
+                return list(_p.fallback_models)
+    except Exception:
+        pass
+
     curated_static = list(_PROVIDER_MODELS.get(normalized, []))
     if normalized in _MODELS_DEV_PREFERRED:
         return _merge_with_models_dev(normalized, curated_static)