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>

tests/droid-writer.test.ts

@@ -0,0 +1,100 @@
+import { describe, expect, test } from "bun:test"
+import { promises as fs } from "fs"
+import path from "path"
+import os from "os"
+import { writeDroidBundle } from "../src/targets/droid"
+import type { DroidBundle } from "../src/types/droid"
+
+async function exists(filePath: string): Promise<boolean> {
+  try {
+    await fs.access(filePath)
+    return true
+  } catch {
+    return false
+  }
+}
+
+describe("writeDroidBundle", () => {
+  test("writes commands, droids, and skills", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "droid-test-"))
+    const bundle: DroidBundle = {
+      commands: [{ name: "plan", content: "Plan command content" }],
+      droids: [{ name: "security-reviewer", content: "Droid content" }],
+      skillDirs: [
+        {
+          name: "skill-one",
+          sourceDir: path.join(import.meta.dir, "fixtures", "sample-plugin", "skills", "skill-one"),
+        },
+      ],
+    }
+
+    await writeDroidBundle(tempRoot, bundle)
+
+    expect(await exists(path.join(tempRoot, ".factory", "commands", "plan.md"))).toBe(true)
+    expect(await exists(path.join(tempRoot, ".factory", "droids", "security-reviewer.md"))).toBe(true)
+    expect(await exists(path.join(tempRoot, ".factory", "skills", "skill-one", "SKILL.md"))).toBe(true)
+
+    const commandContent = await fs.readFile(
+      path.join(tempRoot, ".factory", "commands", "plan.md"),
+      "utf8",
+    )
+    expect(commandContent).toContain("Plan command content")
+
+    const droidContent = await fs.readFile(
+      path.join(tempRoot, ".factory", "droids", "security-reviewer.md"),
+      "utf8",
+    )
+    expect(droidContent).toContain("Droid content")
+  })
+
+  test("writes directly into a .factory output root", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "droid-home-"))
+    const factoryRoot = path.join(tempRoot, ".factory")
+    const bundle: DroidBundle = {
+      commands: [{ name: "plan", content: "Plan content" }],
+      droids: [{ name: "reviewer", content: "Reviewer content" }],
+      skillDirs: [],
+    }
+
+    await writeDroidBundle(factoryRoot, bundle)
+
+    expect(await exists(path.join(factoryRoot, "commands", "plan.md"))).toBe(true)
+    expect(await exists(path.join(factoryRoot, "droids", "reviewer.md"))).toBe(true)
+    // Should not double-nest under .factory/.factory
+    expect(await exists(path.join(factoryRoot, ".factory"))).toBe(false)
+  })
+
+  test("handles empty bundles gracefully", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "droid-empty-"))
+    const bundle: DroidBundle = {
+      commands: [],
+      droids: [],
+      skillDirs: [],
+    }
+
+    await writeDroidBundle(tempRoot, bundle)
+
+    // Root should exist but no subdirectories created
+    expect(await exists(tempRoot)).toBe(true)
+  })
+
+  test("writes multiple commands as separate files", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "droid-multi-"))
+    const factoryRoot = path.join(tempRoot, ".factory")
+    const bundle: DroidBundle = {
+      commands: [
+        { name: "plan", content: "Plan content" },
+        { name: "work", content: "Work content" },
+        { name: "brainstorm", content: "Brainstorm content" },
+      ],
+      droids: [],
+      skillDirs: [],
+    }
+
+    await writeDroidBundle(factoryRoot, bundle)
+
+    expect(await exists(path.join(factoryRoot, "commands", "plan.md"))).toBe(true)
+    expect(await exists(path.join(factoryRoot, "commands", "work.md"))).toBe(true)
+    expect(await exists(path.join(factoryRoot, "commands", "brainstorm.md"))).toBe(true)
+  })
+})