fix: sync skills to correct OpenCode directory

[randomm]

Summary

This is a critical fix for v1.0.1 release. The plugin was syncing skills to the wrong location.

Changes

• Fixed skill sync target directory from ~/.opencode/skill to ~/.config/opencode/skill
• This aligns with the correct OpenCode configuration directory structure
• Makes the plugin functional in OpenCode environments

Impact

Without this fix, synced skills are placed in an incorrect directory that OpenCode doesn't read from, making the plugin non-functional.

[randomm]

This PR proposed changing the skill sync target directory from ~/.claude/skills/ to ~/.config/opencode/skill/. However, investigation confirms:

1. OpenCode supports both directories for skill discovery - both are valid
2. The plugin is working correctly - 96 skills are loading successfully
3. Skills from ~/.claude/skills/ are accessible via the skill loading mechanism
4. No change is needed - current implementation is functioning as designed

The dual-directory support is intentional and allows flexibility in skill installation locations. Closing as not needed.