Fix package index fallback edge case, accept self-name resolution errors under ambiguous project root

[andrewbranch]

Closes #3479
Fixes a porting bug of microsoft/TypeScript#49327
Opened #3775 as a to-do after we move repos

[Copilot]

Pull request overview

This PR adjusts Node-style module resolution to better match upstream TypeScript behavior around "exports": null (not blocking fallback resolution), and updates/accepts baseline differences for module self-name/imports behavior under ambiguous project roots.

Changes:

• Update loadModuleFromSpecificNodeModulesDirectory to treat falsy exports (notably null) as not blocking fallback resolution.
• Promote several module-resolution-related baseline diffs from submoduleTriaged to submoduleAccepted, with notes about rootDir-based follow-ups.
• Update/remove reference baselines to reflect corrected implicit index fallback behavior.

Reviewed changes

Copilot reviewed 7 out of 21 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
internal/module/resolver.go	Adjusts exports-blocking logic to avoid treating "exports": null as blocking fallback resolution.
testdata/submoduleTriaged.txt	Removes the issue #3479 triage block entries now handled/accepted elsewhere.
testdata/submoduleAccepted.txt	Adds accepted baseline diffs for ambiguous-project-root module resolution differences, with follow-up note referencing #3775.
testdata/baselines/reference/submoduleTriaged/compiler/nodeNextImportModeImplicitIndexResolution2.errors.txt.diff	Removes an obsolete triaged diff now resolved by updated resolver behavior.
testdata/baselines/reference/submoduleAccepted/compiler/nodeNextPackageSelfNameWithOutDir.errors.txt.diff	Adds accepted baseline diff for self-name resolution under ambiguous project root.
testdata/baselines/reference/submoduleAccepted/compiler/nodeNextPackageSelfNameWithOutDirDeclDir.errors.txt.diff	Adds accepted baseline diff for self-name resolution under ambiguous project root (declDir variant).
testdata/baselines/reference/submoduleAccepted/conformance/nodeAllowJsPackageSelfName(module=node16).errors.txt.diff	Adds accepted baseline diff for allowJs self-name resolution under ambiguous project root.
testdata/baselines/reference/submoduleAccepted/conformance/nodeAllowJsPackageSelfName(module=node18).errors.txt.diff	Same as above for node18.
testdata/baselines/reference/submoduleAccepted/conformance/nodeAllowJsPackageSelfName(module=node20).errors.txt.diff	Same as above for node20.
testdata/baselines/reference/submoduleAccepted/conformance/nodeAllowJsPackageSelfName(module=nodenext).errors.txt.diff	Same as above for nodenext.
testdata/baselines/reference/submoduleAccepted/conformance/nodeModulesAllowJsPackageImports(module=node16).errors.txt.diff	Adds accepted baseline diff for imports map resolution under ambiguous project root (node16).
testdata/baselines/reference/submoduleAccepted/conformance/nodeModulesAllowJsPackageImports(module=node18).errors.txt.diff	Same as above for node18.
testdata/baselines/reference/submoduleAccepted/conformance/nodeModulesAllowJsPackageImports(module=node20).errors.txt.diff	Same as above for node20.
testdata/baselines/reference/submoduleAccepted/conformance/nodeModulesAllowJsPackageImports(module=nodenext).errors.txt.diff	Same as above for nodenext.
testdata/baselines/reference/submoduleAccepted/conformance/nodeModulesDeclarationEmitWithPackageExports(module=node16).errors.txt.diff	Adds accepted baseline diff for package exports + declaration emit under ambiguous project root (node16).
testdata/baselines/reference/submoduleAccepted/conformance/nodeModulesDeclarationEmitWithPackageExports(module=node18).errors.txt.diff	Same as above for node18.
testdata/baselines/reference/submoduleAccepted/conformance/nodeModulesDeclarationEmitWithPackageExports(module=node20).errors.txt.diff	Same as above for node20.
testdata/baselines/reference/submoduleAccepted/conformance/nodeModulesDeclarationEmitWithPackageExports(module=nodenext).errors.txt.diff	Same as above for nodenext.
testdata/baselines/reference/submodule/compiler/nodeNextImportModeImplicitIndexResolution2.types.diff	Removes an obsolete diff now aligned with the updated resolution behavior.
testdata/baselines/reference/submodule/compiler/nodeNextImportModeImplicitIndexResolution2.types	Updates expected type output now that the module resolves correctly.
testdata/baselines/reference/submodule/compiler/nodeNextImportModeImplicitIndexResolution2.errors.txt	Updates expected diagnostics now that the module resolves correctly.