fix(deps): resolve subpath extensions for packages without exports field

[sxzz]

• This PR contains AI-generated code, but I have carefully reviewed it myself. Otherwise, my PR may be closed.

Description

When a dependency has no exports field in its package.json, subpath imports like source-map-support/register need to be resolved to their actual file path (e.g. source-map-support/register.js) for valid ESM output.

Key changes in src/features/deps.ts:

• Rename DepPlugin → DepsPlugin for consistency with the module name (deps.ts)
• Resolve dependency IDs upfront via this.resolve() and pass the ResolvedId to externalStrategy, avoiding redundant resolution in skipNodeModulesBundle
• Add resolveDepPath(): when a dependency subpath import (e.g. foo/bar) resolves to a package without an exports field, rewrite the import to include the file extension (e.g. foo/bar.js)
• externalStrategy can now return [true, resolvedId] to indicate external with a rewritten import path
• Extract parseDepPath() as a shared utility used by both parseBundledDep and resolveDepPath
• When shouldExternal is not explicitly set but resolved exists, forward the resolved result with moduleSideEffects

Other changes:

• Update imports in src/features/rolldown.ts and src/plugins.ts to use DepsPlugin
• Remove unused @publint/pack dev dependency from package.json, pnpm-workspace.yaml, and tsdown.config.ts

Linked Issues

Closes #854

Additional context

The resolveDepPath function works by:

1. Checking if the resolved module has a packageJsonPath (from Rolldown's resolver)
2. Skipping if the import already has a file extension or has no subpath
3. Reading the package's package.json to check for an exports field
4. If no exports field exists, using the actual resolved file path to construct the correct import specifier with extension

[netlify]

✅ Deploy Preview for tsdown-main ready!

Name	Link
🔨 Latest commit	fc1bc20
🔍 Latest deploy log	https://app.netlify.com/projects/tsdown-main/deploys/69c3a7b55192140008b03da4
😎 Deploy Preview	https://deploy-preview-863--tsdown-main.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[pkg-pr-new]

Open in StackBlitz

tsdown

pnpm add https://pkg.pr.new/tsdown@863 -D

npm i https://pkg.pr.new/tsdown@863 -D

yarn add https://pkg.pr.new/tsdown@863.tgz -D

create-tsdown

pnpm add https://pkg.pr.new/create-tsdown@863 -D

npm i https://pkg.pr.new/create-tsdown@863 -D

yarn add https://pkg.pr.new/create-tsdown@863.tgz -D

@tsdown/css

pnpm add https://pkg.pr.new/@tsdown/css@863 -D

npm i https://pkg.pr.new/@tsdown/css@863 -D

yarn add https://pkg.pr.new/@tsdown/css@863.tgz -D

@tsdown/exe

pnpm add https://pkg.pr.new/@tsdown/exe@863 -D

npm i https://pkg.pr.new/@tsdown/exe@863 -D

yarn add https://pkg.pr.new/@tsdown/exe@863.tgz -D

tsdown-migrate

pnpm add https://pkg.pr.new/tsdown-migrate@863 -D

npm i https://pkg.pr.new/tsdown-migrate@863 -D

yarn add https://pkg.pr.new/tsdown-migrate@863.tgz -D

commit: 10c21de