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/mlops/saelens/references/README.md

@@ -0,0 +1,70 @@
+# SAELens Reference Documentation
+
+This directory contains comprehensive reference materials for SAELens.
+
+## Contents
+
+- [api.md](api.md) - Complete API reference for SAE, TrainingSAE, and configuration classes
+- [tutorials.md](tutorials.md) - Step-by-step tutorials for training and analyzing SAEs
+- [papers.md](papers.md) - Key research papers on sparse autoencoders
+
+## Quick Links
+
+- **GitHub Repository**: https://github.com/jbloomAus/SAELens
+- **Neuronpedia**: https://neuronpedia.org (browse pre-trained SAE features)
+- **HuggingFace SAEs**: Search for tag `saelens`
+
+## Installation
+
+```bash
+pip install sae-lens
+```
+
+Requirements: Python 3.10+, transformer-lens>=2.0.0
+
+## Basic Usage
+
+```python
+from transformer_lens import HookedTransformer
+from sae_lens import SAE
+
+# Load model and SAE
+model = HookedTransformer.from_pretrained("gpt2-small", device="cuda")
+sae, cfg_dict, sparsity = SAE.from_pretrained(
+    release="gpt2-small-res-jb",
+    sae_id="blocks.8.hook_resid_pre",
+    device="cuda"
+)
+
+# Encode activations to sparse features
+tokens = model.to_tokens("Hello world")
+_, cache = model.run_with_cache(tokens)
+activations = cache["resid_pre", 8]
+
+features = sae.encode(activations)  # Sparse feature activations
+reconstructed = sae.decode(features)  # Reconstructed activations
+```
+
+## Key Concepts
+
+### Sparse Autoencoders
+SAEs decompose dense neural activations into sparse, interpretable features:
+- **Encoder**: Maps d_model → d_sae (typically 4-16x expansion)
+- **ReLU/TopK**: Enforces sparsity
+- **Decoder**: Reconstructs original activations
+
+### Training Loss
+`Loss = MSE(original, reconstructed) + L1_coefficient × L1(features)`
+
+### Key Metrics
+- **L0**: Average number of active features (target: 50-200)
+- **CE Loss Score**: Cross-entropy recovered vs original model (target: 80-95%)
+- **Dead Features**: Features that never activate (target: <5%)
+
+## Available Pre-trained SAEs
+
+| Release | Model | Description |
+|---------|-------|-------------|
+| `gpt2-small-res-jb` | GPT-2 Small | Residual stream SAEs |
+| `gemma-2b-res` | Gemma 2B | Residual stream SAEs |
+| Various | Search HuggingFace | Community-trained SAEs |