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/commands/workflows/work.md

@@ -1,10 +0,0 @@
----
-name: workflows:work
-description: "[DEPRECATED] Use /ce:work instead — renamed for clarity."
-argument-hint: "[plan file, specification, or todo file path]"
-disable-model-invocation: true
----
-
-NOTE: /workflows:work is deprecated. Please use /ce:work instead. This alias will be removed in a future version.
-
-/ce:work $ARGUMENTS