fix(targets): nest colon-separated command names into directories

[mvanhorn]

Summary

• Fix Windows/NTFS compatibility by splitting colon-separated command names (e.g. ce:plan) into nested directories (e.g. ce/plan.md) instead of using colons in filenames
• Applied to opencode, droid, and gemini targets
• Matches the approach already used by the Qwen target (src/targets/qwen.ts:35-41)

Fixes #226

Changes

src/targets/opencode.ts: Split commandFile.name on : and create nested directories
src/targets/droid.ts: Same fix
src/targets/gemini.ts: Same fix (uses .toml extension)

Before

commands/ce:plan.md      # Invalid on Windows/NTFS
commands/ce:work.md
commands/ce:review.md

After

commands/ce/plan.md      # Valid on all platforms
commands/ce/work.md
commands/ce/review.md

Commands without colons (e.g. deepen-plan, triage) are unaffected.

Test plan

• bun test passes (312/312 existing tests pass)
• Install plugin to opencode target on Windows and verify ce:* commands appear
• Verify non-colon commands still work correctly

This contribution was developed with AI assistance (Claude Code).

[tmchow]

@mvanhorn is this even relevant anymore given the restructuring in #241? Or do you think it's still worthwhile for future proofing?

[mvanhorn]

Good question! #251 is still relevant - it fixes the install targets (opencode, droid, gemini), not the source layout. After #241, the skill name: frontmatter still uses colons (e.g., ce:plan), and when targets write these to disk, NTFS rejects colons in filenames. #251 splits those into nested directories at install time, matching what the Qwen target already does. Happy to close if you'd prefer a different approach though.