Add unified scripts system with find-skills and run

Consolidates skill discovery and adds generic runner for cross-platform compatibility.

Changes:
- Created scripts/find-skills: Unified tool (show all + filter by pattern)
  - Shows descriptions by default
  - Searches personal first, then core (shadowing)
  - Logs searches for gap analysis
  - Bash 3.2 compatible

- Created scripts/run: Generic runner for any skill script
  - Searches personal superpowers first, then core
  - Enables running arbitrary skill scripts without CLAUDE_PLUGIN_ROOT env var
  - Example: scripts/run skills/collaboration/remembering-conversations/tool/search-conversations

- Fixed bash 3.2 compatibility in list-skills, skills-search
  - Replaced associative arrays with newline-delimited lists
  - Works on macOS default bash (3.2) and Linux bash 4+

- Updated all documentation to reference scripts/find-skills
- Removed redundant wrapper scripts

This solves the CLAUDE_PLUGIN_ROOT environment variable issue - scripts
can now be called from anywhere without needing the env var set.

skills/meta/writing-skills/SKILL.md

@@ -576,7 +576,7 @@ Deploying untested skills = deploying untested code. It's a violation of quality
 How future Claude finds your skill:
 
 1. **Encounters problem** ("tests are flaky")
-2. **Searches skills** using `skills-search` tool (checks personal then core)
+2. **Searches skills** using `find-skills` tool (checks personal then core)
 3. **Finds SKILL.md** (rich when_to_use matches)
 4. **Scans overview** (is this relevant?)
 5. **Reads patterns** (quick reference table)