feat(factory): add native Droid plugin packaging (#120)

* feat(factory): add native Droid plugin packaging

* test(factory): guard documented install contract

* fix(factory): enforce install command order

skills/diagram-design/references/onboarding.md

@@ -198,6 +198,12 @@ Use the installed-skill location exposed by the current agent when available. Ot
 1. `~/.claude/skills/<skill-name>/` (user install)
 2. `.claude/skills/<skill-name>/` (project install)
 
+**Factory Droid:**
+
+1. `~/.factory/skills/<skill-name>/` (personal install)
+2. `.factory/skills/<skill-name>/` from the current directory through the repo root (folder-specific or project install)
+3. The active path shown in `/skills` under **Plugins**; installed plugins keep the shared `skills/<skill-name>/` directory inside Droid's plugin cache
+
 Finally, check any path the user provides explicitly. If the skill is still not found, ask the user to confirm the name or provide its path.
 
 ### Step 2 — read token sources