Fix dependency resolution: subpath imports, DTS generation, and bundle deduplication

[titouanmathis]

Summary

Fixes #57 — three related issues in the dependency resolution and bundling pipeline.

1. Subpath specifier handling in resolveDependencies

Problem: For a dependency like @studiometa/js-toolkit/utils, the version was looked up using the full specifier (not found) and the esm.sh URL was incorrectly formatted as esm.sh/@studiometa/js-toolkit/utils@3.4.3 (404).

Fix: Added getPackageName() and getSubpath() helpers that correctly split specifiers. The esm.sh URL is now formatted as esm.sh/@studiometa/js-toolkit@3.4.3/utils.

2. DTS generation silently fails for npm package source values

Problem: Using source: "morphdom" (a bare npm package name) creates a temporary re-export entry that falls outside tsconfig include paths, causing tsdown to silently skip DTS generation.

Fix: Bare npm package names are now rejected as source values with a clear warning. They fall back to esm.sh resolution automatically. The DependencyConfig type JSDoc has been updated to clarify that source only supports local file paths/globs.

3. Self-hosted bundles inline all dependencies, causing duplication

Problem: When @studiometa/ui is self-hosted, tsdown inlines all its dependencies into the output bundle. If those same dependencies are also imported via esm.sh, the browser ends up with two separate instances.

Fix: The plugin now auto-externalizes any specifier that already exists in the import map. The preset passes Object.keys(mergedImportMap) to the plugin constructor so self-hosted bundles emit import ... from "@studiometa/js-toolkit" instead of inlining — the browser's import map resolves it at runtime.

Changes

• resolve-dependencies.ts: New getPackageName, getSubpath, isLocalSource helpers; fixed esm.sh URL construction; bare npm source rejection with warning
• PlaygroundDependenciesPlugin.ts: New importMapKeys constructor parameter; pass external to tsdown build
• playground.ts preset: Pass Object.keys(mergedImportMap) to the plugin
• Tests: 75 tests passing — new coverage for subpath imports, npm source rejection, importMapKeys
• README.md: Document subpath imports, clarify source field, add bundle deduplication section, remove duplicated/outdated docs

[github-actions]

Export Size

Unchanged

@studiometa/playground

Name	Size	Diff
createPlayground	1 B	-
unzip	1 B	-
zip	1 B	-

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Latest commit:	2f6994f
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View logs

[codecov]

Codecov Report

❌ Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 17.82%. Comparing base (a2966bb) to head (2f6994f).
⚠️ Report is 2 commits behind head on develop.

Files with missing lines	Patch %	Lines
...nd/src/lib/plugins/PlaygroundDependenciesPlugin.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #58      +/-   ##
===========================================
+ Coverage    16.04%   17.82%   +1.77%     
===========================================
  Files           53       53              
  Lines          916      937      +21     
  Branches       156      165       +9     
===========================================
+ Hits           147      167      +20     
- Misses         756      757       +1     
  Partials        13       13              

Flag	Coverage Δ
unittests	17.82% <95.65%> (+1.77%)	⬆️

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