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/main.py

@@ -1611,6 +1611,21 @@ def cmd_model(args):
     select_provider_and_model(args=args)
 
 
+def _is_profile_api_key_provider(provider_id: str) -> bool:
+    """Return True when provider_id maps to a profile with auth_type='api_key'.
+
+    Used as a catch-all in select_provider_and_model() so that new providers
+    declared in providers/*.py automatically dispatch to _model_flow_api_key_provider
+    without requiring an explicit elif branch here.
+    """
+    try:
+        from providers import get_provider_profile
+        _p = get_provider_profile(provider_id)
+        return _p is not None and _p.auth_type == "api_key"
+    except Exception:
+        return False
+
+
 def select_provider_and_model(args=None):
     """Core provider selection + model picking logic.
 
@@ -1907,7 +1922,7 @@ def select_provider_and_model(args=None):
         "ollama-cloud",
         "tencent-tokenhub",
         "lmstudio",
-    ):
+    ) or _is_profile_api_key_provider(selected_provider):
         _model_flow_api_key_provider(config, selected_provider, current_model)
 
     # ── Post-switch cleanup: clear stale OPENAI_BASE_URL ──────────────
@@ -8215,6 +8230,22 @@ def cmd_logs(args):
     )
 
 
+def _build_provider_choices() -> list[str]:
+    """Build the --provider choices list from CANONICAL_PROVIDERS + 'auto'."""
+    try:
+        from hermes_cli.models import CANONICAL_PROVIDERS as _cp
+        return ["auto"] + [p.slug for p in _cp]
+    except Exception:
+        # Fallback: static list guarantees the CLI always works
+        return [
+            "auto", "openrouter", "nous", "openai-codex", "copilot-acp", "copilot",
+            "anthropic", "gemini", "google-gemini-cli", "xai", "bedrock", "azure-foundry",
+            "ollama-cloud", "huggingface", "zai", "kimi-coding", "kimi-coding-cn",
+            "stepfun", "minimax", "minimax-cn", "kilocode", "xiaomi", "arcee",
+            "nvidia", "deepseek", "alibaba", "qwen-oauth", "opencode-zen", "opencode-go",
+        ]
+
+
 def main():
     """Main entry point for hermes CLI."""
     from hermes_cli._parser import build_top_level_parser