Add new skills descriptions and enhance skills tool functionality

- Added detailed descriptions for new skills categories: Machine Learning Operations and Note Taking.
- Introduced a new Obsidian skill with commands for reading, listing, searching, creating, and appending notes.
- Enhanced the skills tool to load and display category descriptions from DESCRIPTION.md files, improving user guidance and discovery of available skills.

skills/mlops/DESCRIPTION.md

@@ -0,0 +1,3 @@
+---
+description: Knowledge and Tools for Machine Learning Operations - tools and frameworks for training, fine-tuning, deploying, and optimizing ML/AI models
+---

skills/note-taking/DESCRIPTION.md

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+---
+description: Note taking skills, to save information, assist with research, and collab on multi-session planning and information sharing.
+---

skills/note-taking/obsidian/SKILL.md

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+---
+name: obsidian
+description: Read, search, and create notes in the Obsidian vault.
+---
+
+# Obsidian Vault
+
+**Location:** `/home/teknium/Documents/Primary Vault`
+
+Note: Path contains a space - always quote it.
+
+## Read a note
+
+```bash
+cat "/home/teknium/Documents/Primary Vault/Note Name.md"
+```
+
+## List notes
+
+```bash
+# All notes
+find "/home/teknium/Documents/Primary Vault" -name "*.md" -type f
+
+# In a specific folder
+ls "/home/teknium/Documents/Primary Vault/AI Research/"
+```
+
+## Search
+
+```bash
+# By filename
+find "/home/teknium/Documents/Primary Vault" -name "*.md" -iname "*keyword*"
+
+# By content
+grep -rli "keyword" "/home/teknium/Documents/Primary Vault" --include="*.md"
+```
+
+## Create a note
+
+```bash
+cat > "/home/teknium/Documents/Primary Vault/New Note.md" << 'ENDNOTE'
+# Title
+
+Content here.
+ENDNOTE
+```
+
+## Append to a note
+
+```bash
+echo "
+New content here." >> "/home/teknium/Documents/Primary Vault/Existing Note.md"
+```
+
+## Wikilinks
+
+Obsidian links notes with `[[Note Name]]` syntax. When creating notes, use these to link related content.