refactor(skills): migrate commands to skills directory structure

Move all 27 command .md files from commands/ to skills/*/SKILL.md
format. Claude Code 2.1.3+ merged commands and skills - both create
slash commands and work identically. Skills add optional features
like supporting files and automatic context loading.

- commands/ce/*.md -> skills/ce-*/SKILL.md
- commands/workflows/*.md -> skills/workflows-*/SKILL.md
- commands/*.md -> skills/*/SKILL.md
- Update plugin.json and marketplace.json descriptions
- Update CLAUDE.md directory structure docs
- Update deploy-docs and generate_command references

Fixes #116

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/compound-engineering/skills/workflows-compound/SKILL.md

@@ -0,0 +1,10 @@
+---
+name: workflows:compound
+description: "[DEPRECATED] Use /ce:compound instead — renamed for clarity."
+argument-hint: "[optional: brief context about the fix]"
+disable-model-invocation: true
+---
+
+NOTE: /workflows:compound is deprecated. Please use /ce:compound instead. This alias will be removed in a future version.
+
+/ce:compound $ARGUMENTS