refactor(commands): replace SlashCommand with Skill tool invocation

Update all workflow command files to use Skill tool instead of SlashCommand:
- Change allowed-tools: SlashCommand(*) → Skill(*)
- Convert SlashCommand(command="/path", args="...") → Skill(skill="path", args="...")
- Update descriptive text references from SlashCommand to Skill
- Remove javascript language tags from code blocks (25 files)

Affected 25 command files across:
- workflow: plan, execute, init, lite-plan, lite-fix, etc.
- workflow/test: test-fix-gen, test-cycle-execute, tdd-plan, tdd-verify
- workflow/review: review-cycle-fix, review-module-cycle, review-session-cycle
- workflow/ui-design: codify-style, explore-auto, imitate-auto
- workflow/brainstorm: brainstorm-with-file, auto-parallel
- issue: discover, discover-by-prompt, plan
- ccw, ccw-debug

This aligns with the actual Skill tool interface which uses 'skill' and 'args' parameters.

.claude/commands/issue/plan.md

@@ -2,7 +2,7 @@
 name: plan
 description: Batch plan issue resolution using issue-plan-agent (explore + plan closed-loop)
 argument-hint: "[-y|--yes] --all-pending <issue-id>[,<issue-id>,...] [--batch-size 3]"
-allowed-tools: TodoWrite(*), Task(*), SlashCommand(*), AskUserQuestion(*), Bash(*), Read(*), Write(*)
+allowed-tools: TodoWrite(*), Task(*), Skill(*), AskUserQuestion(*), Bash(*), Read(*), Write(*)
 ---
 
 ## Auto Mode