chore(skills): move heavy training skills + outlines to optional-skills (#22912)

These skills require heavy GPU/CUDA stacks or are niche enough that they shouldn't
be active by default. Moved to optional-skills/ where users opt-in via
`hermes skills install official/...`.

Moved:
- mlops/training/axolotl
- mlops/training/trl-fine-tuning
- mlops/training/unsloth
- mlops/inference/outlines

Counts: 91 -> 87 built-in, 72 -> 76 optional.

Auto-regenerated docs (per-skill pages + catalogs) reflect the move.

optional-skills/mlops/training/axolotl/references/index.md

@@ -0,0 +1,15 @@
+# Axolotl Documentation Index
+
+## Categories
+
+### Api
+**File:** `api.md`
+**Pages:** 150
+
+### Dataset-Formats
+**File:** `dataset-formats.md`
+**Pages:** 9
+
+### Other
+**File:** `other.md`
+**Pages:** 26