Split long vertical chains into smaller clustered subgraphs

- Add subgraph cluster styling (style <id> fill:#HEX after each 'end')
- Split area_2 (Isle of Wonder) into 3 subgraphs: Gnomes, Garden & Beach, Chessboard & Trades
- Split area_3 (Isle of Beast) into 2 subgraphs: Approach & Maze, Dark Passage & Minotaur
- Split area_5 (SacRED MOUNTAIN) into 2 subgraphs: Cliffs/Cave/Poison, Spell Components
- Split area_7 (Realm of Dead) into 3 subgraphs: Arrival & Zombies, Gate & Charon, Death & Return

Total subgraphs increased from 8 to 14 for better line clustering.
Lines now average ~10-15 nodes per subgraph instead of 30-60.

Also update skills:
- Document subgraph cluster styling requirement (style <id> after 'end')
- Add cluster size guidance (aim for 10-20 nodes per subgraph)

.opencode/skills/qa-dependency-graph/SKILL.md

@@ -80,6 +80,7 @@ ACTION: Trade with pawn broker
 - [ ] Areas use index-based color palette
 - [ ] **FLAT STRUCTURE**: No nested subgraphs - all subgraphs at same level
 - [ ] **Same Area = Same Color**: If area appears twice (start AND end), use SAME color
+- [ ] **Subgraph Cluster Styling**: Each subgraph must have a `style <id> fill:#HEX,stroke:#STROKE` command AFTER its `end` to color the container itself
 
 ## Dangling Node Detection