feat(gateway): skill-aware slash commands, paginated /commands, Telegram 100-cap (#3934)

* feat(gateway): skill-aware slash commands, paginated /commands, Telegram 100-cap

Map active skills to Telegram's slash command menu so users can
discover and invoke skills directly. Three changes:

1. Telegram menu now includes active skill commands alongside built-in
   commands, capped at 100 entries (Telegram Bot API limit). Overflow
   commands remain callable but hidden from the picker. Logged at
   startup when cap is hit.

2. New /commands [page] gateway command for paginated browsing of all
   commands + skills. /help now shows first 10 skill commands and
   points to /commands for the full list.

3. When a user types a slash command that matches a disabled or
   uninstalled skill, they get actionable guidance:
   - Disabled: 'Enable it with: hermes skills config'
   - Optional (not installed): 'Install with: hermes skills install official/<path>'

Built on ideas from PR #3921 by @kshitijk4poor.

* chore: move 21 niche skills to optional-skills

Move specialized/niche skills from built-in (skills/) to optional
(optional-skills/) to reduce the default skill count. Users can
install them with: hermes skills install official/<category>/<name>

Moved skills (21):
- mlops: accelerate, chroma, faiss, flash-attention,
  hermes-atropos-environments, huggingface-tokenizers, instructor,
  lambda-labs, llava, nemo-curator, pinecone, pytorch-lightning,
  qdrant, saelens, simpo, slime, tensorrt-llm, torchtitan
- research: domain-intel, duckduckgo-search
- devops: inference-sh cli

Built-in skills: 96 → 75
Optional skills: 22 → 43

* fix: only include repo built-in skills in Telegram menu, not user-installed

User-installed skills (from hub or manually added) stay accessible via
/skills and by typing the command directly, but don't get registered
in the Telegram slash command picker. Only skills whose SKILL.md is
under the repo's skills/ directory are included in the menu.

This keeps the Telegram menu focused on the curated built-in set while
user-installed skills remain discoverable through /skills and /commands.

optional-skills/devops/cli/references/authentication.md

@@ -0,0 +1,59 @@
+# Authentication & Setup
+
+## Install the CLI
+
+```bash
+curl -fsSL https://cli.inference.sh | sh
+```
+
+## Login
+
+```bash
+infsh login
+```
+
+This opens a browser for authentication. After login, credentials are stored locally.
+
+## Check Authentication
+
+```bash
+infsh me
+```
+
+Shows your user info if authenticated.
+
+## Environment Variable
+
+For CI/CD or scripts, set your API key:
+
+```bash
+export INFSH_API_KEY=your-api-key
+```
+
+The environment variable overrides the config file.
+
+## Update CLI
+
+```bash
+infsh update
+```
+
+Or reinstall:
+
+```bash
+curl -fsSL https://cli.inference.sh | sh
+```
+
+## Troubleshooting
+
+| Error | Solution |
+|-------|----------|
+| "not authenticated" | Run `infsh login` |
+| "command not found" | Reinstall CLI or add to PATH |
+| "API key invalid" | Check `INFSH_API_KEY` or re-login |
+
+## Documentation
+
+- [CLI Setup](https://inference.sh/docs/extend/cli-setup) - Complete CLI installation guide
+- [API Authentication](https://inference.sh/docs/api/authentication) - API key management
+- [Secrets](https://inference.sh/docs/secrets/overview) - Managing credentials