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/reference/optional-skills-catalog.md

@@ -54,6 +54,7 @@ hermes skills uninstall <skill-name>
 | Skill | Description |
 |-------|-------------|
 | **blender-mcp** | Control Blender directly from Hermes via socket connection to the blender-mcp addon. Create 3D objects, materials, animations, and run arbitrary Blender Python (bpy) code. |
+| **concept-diagrams** | Generate flat, minimal light/dark-aware SVG diagrams as standalone HTML files, using a unified educational visual language (9 semantic color ramps, automatic dark mode). Best for physics setups, chemistry mechanisms, math curves, physical objects (aircraft, turbines, smartphones), floor plans, cross-sections, lifecycle/process narratives, and hub-spoke system diagrams. Ships with 15 example diagrams. |
 | **meme-generation** | Generate real meme images by picking a template and overlaying text with Pillow. Produces actual `.png` meme files. |
 
 ## DevOps