feat(providers): make all 33 providers pluggable under plugins/model-providers/

Every provider profile is now a self-contained plugin under
plugins/model-providers/<name>/, mirroring the plugins/platforms/
pattern established for IRC and Teams. The ProviderProfile ABC
stays in providers/; the per-provider profile data moves out.

- plugins/model-providers/<name>/__init__.py calls register_provider()
- plugins/model-providers/<name>/plugin.yaml declares kind: model-provider
- providers/__init__.py._discover_providers() lazily scans bundled plugins
  then $HERMES_HOME/plugins/model-providers/<name>/ (user override path)
- User plugins with the same name override bundled ones (last-writer-wins
  in register_provider)
- Legacy providers/<name>.py layout still supported for back-compat with
  out-of-tree editable installs
- Hermes PluginManager: new kind=model-provider; skipped like memory
  plugins (providers/ discovery owns them); standalone plugins with
  register_provider+ProviderProfile in their __init__.py auto-coerce to
  this kind (same heuristic as memory providers)
- skip_names extended to include 'model-providers' so the general
  PluginManager doesn't double-scan the category
- 4 new tests in tests/providers/test_plugin_discovery.py covering
  bundled discovery, user override, and general-loader isolation
- Docs updated: website/docs/developer-guide/adding-providers.md,
  provider-runtime.md, providers/README.md, plugins/model-providers/README.md

No API break: auth.py / config.py / doctor.py / models.py / runtime_provider.py /
model_metadata.py / auxiliary_client.py / chat_completions.py / run_agent.py
all still consume providers via get_provider_profile() / list_providers() —
they just now see plugin-discovered entries instead of pkgutil-iterated ones.

Third parties can now drop a single directory into
~/.hermes/plugins/model-providers/<name>/ to add or override an inference
provider without touching the repo.

plugins/model-providers/kimi-coding/__init__.py

@@ -0,0 +1,71 @@
+"""Kimi / Moonshot provider profiles.
+
+Kimi has dual endpoints:
+  - sk-kimi-* keys → api.kimi.com/coding (Anthropic Messages API)
+  - legacy keys → api.moonshot.ai/v1 (OpenAI chat completions)
+
+This module covers the chat_completions path (/v1 endpoint).
+"""
+
+from typing import Any
+
+from providers import register_provider
+from providers.base import OMIT_TEMPERATURE, ProviderProfile
+
+
+class KimiProfile(ProviderProfile):
+    """Kimi/Moonshot — temperature omitted, thinking + reasoning_effort."""
+
+    def build_api_kwargs_extras(
+        self, *, reasoning_config: dict | None = None, **context
+    ) -> tuple[dict[str, Any], dict[str, Any]]:
+        """Kimi uses extra_body.thinking + top-level reasoning_effort."""
+        extra_body = {}
+        top_level = {}
+
+        if not reasoning_config or not isinstance(reasoning_config, dict):
+            # No config → thinking enabled, default effort
+            extra_body["thinking"] = {"type": "enabled"}
+            top_level["reasoning_effort"] = "medium"
+            return extra_body, top_level
+
+        enabled = reasoning_config.get("enabled", True)
+        if enabled is False:
+            extra_body["thinking"] = {"type": "disabled"}
+            return extra_body, top_level
+
+        # Enabled
+        extra_body["thinking"] = {"type": "enabled"}
+        effort = (reasoning_config.get("effort") or "").strip().lower()
+        if effort in ("low", "medium", "high"):
+            top_level["reasoning_effort"] = effort
+        else:
+            top_level["reasoning_effort"] = "medium"
+
+        return extra_body, top_level
+
+
+kimi = KimiProfile(
+    name="kimi-coding",
+    aliases=("kimi", "moonshot", "kimi-for-coding"),
+    env_vars=("KIMI_API_KEY", "KIMI_CODING_API_KEY"),
+    base_url="https://api.moonshot.ai/v1",
+    fixed_temperature=OMIT_TEMPERATURE,
+    default_max_tokens=32000,
+    default_headers={"User-Agent": "hermes-agent/1.0"},
+    default_aux_model="kimi-k2-turbo-preview",
+)
+
+kimi_cn = KimiProfile(
+    name="kimi-coding-cn",
+    aliases=("kimi-cn", "moonshot-cn"),
+    env_vars=("KIMI_CN_API_KEY",),
+    base_url="https://api.moonshot.cn/v1",
+    fixed_temperature=OMIT_TEMPERATURE,
+    default_max_tokens=32000,
+    default_headers={"User-Agent": "hermes-agent/1.0"},
+    default_aux_model="kimi-k2-turbo-preview",
+)
+
+register_provider(kimi)
+register_provider(kimi_cn)