docs: rewrite README, add CHANGELOG, update skill index and roadmap

- README: complete rewrite with all 24 skills, 8 scripts, architecture overview
- CHANGELOG: v0.1.0 → v0.2.0 → v0.3.0 with full feature history
- using-archeflow: updated skill reference to all 24 skills in 6 categories
- plugin.json: version bump to 0.3.0
- roadmap: updated with v0.3.0 features

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "archeflow",
   "description": "Multi-agent orchestration with Jungian archetypes. PDCA quality cycles, shadow detection, git worktree isolation. Zero dependencies — works with any Claude Code session.",
-  "version": "0.1.0",
+  "version": "0.3.0",
   "author": {
     "name": "Chris Nennemann"
   },