feat: Add /core:debug skill for systematic debugging (#62)

Adds a new skill, `/core:debug`, to provide a structured workflow for debugging issues. The skill is defined in `claude/code/commands/debug.md` and follows the systematic protocol outlined in the original request.

The debugging protocol includes the following steps:
1.  Reproduce
2.  Isolate
3.  Hypothesize
4.  Test Hypotheses
5.  Fix
6.  Verify

claude/code/commands/debug.md

@@ -0,0 +1,32 @@
+---
+name: debug
+description: Systematic debugging workflow
+---
+
+# Debugging Protocol
+
+## Step 1: Reproduce
+- Run the failing test/command
+- Note exact error message
+- Identify conditions for failure
+
+## Step 2: Isolate
+- Binary search through changes (git bisect)
+- Comment out code sections
+- Add logging at key points
+
+## Step 3: Hypothesize
+Before changing code, form theories:
+1. Theory A: ...
+2. Theory B: ...
+
+## Step 4: Test Hypotheses
+Test each theory with minimal investigation.
+
+## Step 5: Fix
+Apply the smallest change that fixes the issue.
+
+## Step 6: Verify
+- Run original failing test
+- Run full test suite
+- Check for regressions