fix(config): extract package name from node_modules file:// URLs in getPluginName

[yufeikang]

Issue for this PR

Closes #17716

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

getPluginName returns path.parse(url.pathname).name for file:// URLs, which yields "index" for any plugin whose entry point is index.js/index.ts (the vast majority of npm packages). When load() resolves two npm plugins to file:// paths via import.meta.resolve, deduplicatePlugins sees them both as "index" and silently drops one.

This fix detects /node_modules/ in the file path and extracts the actual npm package name (including scoped packages) instead of the bare filename.

file:///config/node_modules/oh-my-opencode/dist/index.js     → "oh-my-opencode"
file:///config/node_modules/@scope/plugin/dist/index.js      → "@scope/plugin"
file:///path/to/plugin/foo.js                                → "foo" (unchanged)

How did you verify your code works?

• Added unit tests for getPluginName with node_modules paths (unscoped and scoped packages)
• Added unit test for deduplicatePlugins confirming distinct node_modules/*/index.js entries are no longer treated as duplicates
• All existing and new tests pass: bun test test/config/config.test.ts -t "getPluginName|deduplicatePlugins" (10 pass, 0 fail)
• Reproduced the original issue locally: confirmed oh-my-opencode was being dropped due to name collision with opencode-openai-codex-auth (both resolved to "index")

Screenshots / recordings

N/A - no UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

I found several related PRs addressing similar issues with plugin deduplication and file:// URL handling:

Potential Related/Duplicate PRs:

1. fix(opencode): prevent plugin deduplication collision for index.js entry points #11161 - fix(opencode): prevent plugin deduplication collision for index.js entry points

   • fix(opencode): prevent plugin deduplication collision for index.js entry points #11161
   • Directly addresses the same collision issue with index.js entry points

2. fix(config): avoid dedup collisions for file:// plugins in node_modules #15598 - fix(config): avoid dedup collisions for file:// plugins in node_modules

   • fix(config): avoid dedup collisions for file:// plugins in node_modules #15598
   • Specifically handles deduplication collisions for file:// plugins in node_modules

3. fix(config): use package.json name for file:// plugin identity #16200 - fix(config): use package.json name for file:// plugin identity

   • fix(config): use package.json name for file:// plugin identity #16200
   • Uses package.json name for file:// plugin identification, similar approach to the current PR

These PRs appear to be addressing the same or very similar issues with plugin deduplication when resolving file:// URLs in node_modules. Check if any of these were previously closed or merged without fully resolving the issue (issue #17716).

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍