docs: backfill coverage for recently-merged features (#11942)

Fills documentation gaps that accumulated as features merged ahead of their
docs updates. All additions are verified against code and the originating PRs.

Providers:
- Ollama Cloud (#10782) — new provider section, env vars, quickstart/fallback rows
- xAI Grok Responses API + TTS (#10783) — provider note, TTS table + config
- Google Gemini CLI OAuth (#11270) — quickstart/fallback/cli-commands entries
- NVIDIA NIM (#11774) — NVIDIA_API_KEY / NVIDIA_BASE_URL in env-vars reference
- HERMES_INFERENCE_PROVIDER enum updated

Messaging:
- DISCORD_ALLOWED_ROLES (#11608) — env-vars, discord.md access control section
- DingTalk QR device-flow (#11574) — wizard path in Option A + openClaw disclosure
- Feishu document comment intelligent reply (#11898) — full section + 3-tier access control + CLI

Skills / commands:
- concept-diagrams skill (#11363) — optional-skills-catalog entry
- /gquota (#11270) — slash-commands reference

Build: docusaurus build passes, ascii-guard lint 0 errors.

website/docs/user-guide/features/fallback-providers.md

@@ -48,6 +48,9 @@ Both `provider` and `model` are **required**. If either is missing, the fallback
 | MiniMax (China) | `minimax-cn` | `MINIMAX_CN_API_KEY` |
 | DeepSeek | `deepseek` | `DEEPSEEK_API_KEY` |
 | NVIDIA NIM | `nvidia` | `NVIDIA_API_KEY` (optional: `NVIDIA_BASE_URL`) |
+| Ollama Cloud | `ollama-cloud` | `OLLAMA_API_KEY` |
+| Google Gemini (OAuth) | `google-gemini-cli` | `hermes model` (Google OAuth; optional: `HERMES_GEMINI_PROJECT_ID`) |
+| xAI (Grok) | `xai` (alias `grok`) | `XAI_API_KEY` (optional: `XAI_BASE_URL`) |
 | OpenCode Zen | `opencode-zen` | `OPENCODE_ZEN_API_KEY` |
 | OpenCode Go | `opencode-go` | `OPENCODE_GO_API_KEY` |
 | Kilo Code | `kilocode` | `KILOCODE_API_KEY` |

website/docs/user-guide/features/tts.md

@@ -24,6 +24,7 @@ Convert text to speech with seven providers:
 | **MiniMax TTS** | Excellent | Paid | `MINIMAX_API_KEY` |
 | **Mistral (Voxtral TTS)** | Excellent | Paid | `MISTRAL_API_KEY` |
 | **Google Gemini TTS** | Excellent | Free tier | `GEMINI_API_KEY` |
+| **xAI TTS** | Excellent | Paid | `XAI_API_KEY` |
 | **NeuTTS** | Good | Free | None needed |
 
 ### Platform Delivery
@@ -40,7 +41,7 @@ Convert text to speech with seven providers:
 ```yaml
 # In ~/.hermes/config.yaml
 tts:
-  provider: "edge"              # "edge" | "elevenlabs" | "openai" | "minimax" | "mistral" | "gemini" | "neutts"
+  provider: "edge"              # "edge" | "elevenlabs" | "openai" | "minimax" | "mistral" | "gemini" | "xai" | "neutts"
   speed: 1.0                    # Global speed multiplier (provider-specific settings override this)
   edge:
     voice: "en-US-AriaNeural"   # 322 voices, 74 languages
@@ -65,6 +66,12 @@ tts:
   gemini:
     model: "gemini-2.5-flash-preview-tts"  # or gemini-2.5-pro-preview-tts
     voice: "Kore"               # 30 prebuilt voices: Zephyr, Puck, Kore, Enceladus, Gacrux, etc.
+  xai:
+    voice_id: "eve"             # xAI TTS voice (see https://docs.x.ai/docs/api-reference#tts)
+    language: "en"              # ISO 639-1 code
+    sample_rate: 24000          # 22050 / 24000 (default) / 44100 / 48000
+    bit_rate: 128000            # MP3 bitrate; only applies when codec=mp3
+    # base_url: "https://api.x.ai/v1"   # Override via XAI_BASE_URL env var
   neutts:
     ref_audio: ''
     ref_text: ''
@@ -82,6 +89,7 @@ Telegram voice bubbles require Opus/OGG audio format:
 - **Edge TTS** (default) outputs MP3 and needs **ffmpeg** to convert:
 - **MiniMax TTS** outputs MP3 and needs **ffmpeg** to convert for Telegram voice bubbles
 - **Google Gemini TTS** outputs raw PCM and uses **ffmpeg** to encode Opus directly for Telegram voice bubbles
+- **xAI TTS** outputs MP3 and needs **ffmpeg** to convert for Telegram voice bubbles
 - **NeuTTS** outputs WAV and also needs **ffmpeg** to convert for Telegram voice bubbles
 
 ```bash