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/auth.py

@@ -416,6 +416,40 @@ PROVIDER_REGISTRY: Dict[str, ProviderConfig] = {
     ),
 }
 
+# Auto-extend PROVIDER_REGISTRY with any api-key provider registered in
+# providers/ that is not already declared above.  New providers only need a
+# providers/*.py file — no edits to this file required.
+try:
+    from providers import list_providers as _list_providers_for_registry
+    for _pp in _list_providers_for_registry():
+        if _pp.name in PROVIDER_REGISTRY:
+            continue
+        if _pp.auth_type != "api_key" or not _pp.env_vars:
+            continue
+        # Skip providers that need custom token resolution or are special-cased
+        # in resolve_provider() (copilot/kimi/zai have bespoke token refresh;
+        # openrouter/custom are aggregator/user-supplied and handled outside
+        # the registry — adding them here breaks runtime_provider resolution
+        # that relies on `openrouter not in PROVIDER_REGISTRY`).
+        if _pp.name in {"copilot", "kimi-coding", "kimi-coding-cn", "zai", "openrouter", "custom"}:
+            continue
+        _api_key_vars = tuple(v for v in _pp.env_vars if not v.endswith("_BASE_URL") and not v.endswith("_URL"))
+        _base_url_var = next((v for v in _pp.env_vars if v.endswith("_BASE_URL") or v.endswith("_URL")), None)
+        PROVIDER_REGISTRY[_pp.name] = ProviderConfig(
+            id=_pp.name,
+            name=_pp.display_name or _pp.name,
+            auth_type="api_key",
+            inference_base_url=_pp.base_url,
+            api_key_env_vars=_api_key_vars or _pp.env_vars,
+            base_url_env_var=_base_url_var or "",
+        )
+        # Also register aliases so resolve_provider() resolves them
+        for _alias in _pp.aliases:
+            if _alias not in PROVIDER_REGISTRY:
+                PROVIDER_REGISTRY[_alias] = PROVIDER_REGISTRY[_pp.name]
+except Exception:
+    pass
+
 
 # =============================================================================
 # Anthropic Key Helper
@@ -1195,6 +1229,17 @@ def resolve_provider(
         "vllm": "custom", "llamacpp": "custom",
         "llama.cpp": "custom", "llama-cpp": "custom",
     }
+    # Extend with aliases declared in providers/*.py that aren't already mapped.
+    # This keeps providers/ as the single source for new aliases while the
+    # hardcoded dict above remains authoritative for existing ones.
+    try:
+        from providers import list_providers as _lp
+        for _pp in _lp():
+            for _alias in _pp.aliases:
+                if _alias not in _PROVIDER_ALIASES:
+                    _PROVIDER_ALIASES[_alias] = _pp.name
+    except Exception:
+        pass
     normalized = _PROVIDER_ALIASES.get(normalized, normalized)
 
     if normalized == "openrouter":