Fix plugin loading to support JavaScript files and improve error handling

[rmoriz]

Summary

Fixes user reports of plugins not loading by adding JavaScript support and improving error handling in the plugin system. Should fix #1473

Changes

🎯 JavaScript Plugin Support

• Updated plugin discovery glob patterns from plugin/*.ts to plugin/*.{ts,js}
• Both global (~/.config/opencode/plugin/) and project (.opencode/plugin/) directories now support JS files
• Resolves discrepancy where documentation showed JavaScript examples but only TypeScript files were loaded

🛡️ Improved Error Handling

• Replaced try/catch blocks with functional error handling using Promise.catch()
• Added validation for non-function exports to prevent loading invalid plugins
• Implemented resilient loading where one broken plugin doesn't prevent others from loading
• Enhanced error logging with plugin path and specific error details

📚 Documentation Fix

• Corrected hook structure example in documentation to use flat format ("tool.execute.before")
• Previously showed nested object structure that didn't match actual implementation

🔍 Better Debugging

• Added comprehensive logging for each step of plugin initialization
• Clear error messages when plugins fail to import or initialize
• Success confirmations when plugins load correctly

Testing

• All typechecks pass
• Plugin loading logic refactored without breaking existing functionality
• Error handling tested with both valid and invalid plugin scenarios

Impact

This resolves the core issues preventing plugins from working:

1. JavaScript plugins now load - Matches documented behavior
2. Better error visibility - Users can see exactly why plugins fail
3. Robust loading - Plugin system doesn't crash on individual plugin failures
4. Accurate documentation - Examples now work as written

Fixes plugin loading issues reported by users where plugins weren't being discovered or loaded properly.

🤖 Generated with opencode

[imajus]

Very much needed fix, as I faced the issue with JavaScript plugin loading myself. I created a plugin following the official docs but it didn't work. Debugging this issue is quite challenging because the logs don't provide any useful information even with DEBUG level.