Add Factory Droid as a converter target (#174)

Adds a new 'droid' target to the converter that outputs Claude Code plugins
in Factory Droid's format:

- Commands flattened to ~/.factory/commands/ (strips namespace prefixes)
- Agents converted to droids in ~/.factory/droids/ with proper frontmatter
- Skills copied to ~/.factory/skills/
- Content transforms: Task calls, slash commands, and @agent references
  adapted to Droid conventions

This resolves the manual workaround described in issue #31 by automating
the conversion from Claude Code plugin format to Factory Droid's expected
directory structure.

Includes 13 tests covering converter logic and file writer behavior.

Co-authored-by: adamprime <adamprime@hey.com>
Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

src/types/droid.ts

@@ -0,0 +1,20 @@
+export type DroidCommandFile = {
+  name: string
+  content: string
+}
+
+export type DroidAgentFile = {
+  name: string
+  content: string
+}
+
+export type DroidSkillDir = {
+  name: string
+  sourceDir: string
+}
+
+export type DroidBundle = {
+  commands: DroidCommandFile[]
+  droids: DroidAgentFile[]
+  skillDirs: DroidSkillDir[]
+}