fix: use CLAUDE_PLUGIN_ROOT for continuous-learning-v2 paths

Fixes #113

The instinct commands referenced hardcoded paths that only work with
manual installation (~/.claude/skills/...). When installed as a plugin,
files are at ~/.claude/plugins/cache/.../skills/...

Changes:
- Updated instinct-status, instinct-import, evolve commands to use
  ${CLAUDE_PLUGIN_ROOT} with fallback to manual path
- Updated observe.sh hook documentation with both install methods
- Updated SKILL.md with plugin vs manual installation instructions
- Removed duplicate commands from skills/continuous-learning-v2/commands/
  (already exist in commands/)

Users should use ${CLAUDE_PLUGIN_ROOT} in their hooks config when
installed as a plugin.

commands/instinct-import.md

@@ -1,16 +1,23 @@
 ---
 name: instinct-import
 description: Import instincts from teammates, Skill Creator, or other sources
-command: /instinct-import
-implementation: python3 ~/.claude/skills/continuous-learning-v2/scripts/instinct-cli.py import <file>
+command: true
 ---
 
 # Instinct Import Command
 
 ## Implementation
 
+Run the instinct CLI using the plugin root path:
+
 ```bash
-python3 ~/.claude/skills/continuous-learning-v2/scripts/instinct-cli.py import <file-or-url> [--dry-run] [--force] [--min-confidence 0.7]
+python3 "${CLAUDE_PLUGIN_ROOT}/skills/continuous-learning-v2/scripts/instinct-cli.py" import <file-or-url> [--dry-run] [--force] [--min-confidence 0.7]
+```
+
+Or if `CLAUDE_PLUGIN_ROOT` is not set (manual installation):
+
+```bash
+python3 ~/.claude/skills/continuous-learning-v2/scripts/instinct-cli.py import <file-or-url>
 ```
 
 Import instincts from: