languageserver: add .js extensions to imports (ESM prep)

[ericsciple]

Summary

Adds .js extensions to all relative imports in the languageserver package as preparation for ESM migration.

This is a partial migration for package languageserver which is blocked from completing the migration because vscode-languageserver@8.0.2 lacks ESM exports.

Follow-up from PR:

• ESM migration: Add .js extensions for node16 moduleResolution #257

Related Issues:

• Upgrade moduleResolution from node to node16 or nodenext in tsconfig #154
• Published ESM code has imports without file extensions #110
• expressions: ERR_MODULE_NOT_FOUND attempting to run example demo script #64
• Can not import @actions/workflow-parser #146

Changes

• Updated 24 source files in languageserver/src/ to use .js extensions in imports
• Added skipLibCheck: true to languageserver/tsconfig.build.json (required for @types/node compatibility)
• Updated docs/esm-migration-plan.md with current status and documentation
• Synced package-lock.json

Why partial?

Full migration requires moduleResolution: "node16", which fails because vscode-languageserver doesn't have an exports field for subpath imports like vscode-languageserver/node. Once stable v10+ releases with ESM support, we can complete the migration.

[Copilot]

Pull request overview

This PR adds .js extensions to all relative imports in the languageserver package as a preparatory step for ESM migration. The full migration is blocked because vscode-languageserver@8.0.2 lacks proper ESM exports with an exports field for subpath imports.

Key changes:

• Added .js extensions to relative imports across 24 source files in languageserver/src/
• Added skipLibCheck: true to languageserver/tsconfig.build.json to work around type errors in @types/node
• Updated documentation in docs/esm-migration-plan.md to reflect partial migration status

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
languageserver/tsconfig.build.json	Added skipLibCheck: true compiler option
languageserver/src/value-providers/runs-on.ts	Updated relative imports to include .js extensions
languageserver/src/value-providers/job-environment.ts	Updated relative imports to include .js extensions
languageserver/src/value-providers/action-inputs.ts	Updated relative imports to include .js extensions
languageserver/src/value-providers.ts	Updated relative imports to include .js extensions
languageserver/src/utils/username.ts	Updated relative imports to include .js extensions
languageserver/src/utils/repo-permission.ts	Updated relative imports to include .js extensions
languageserver/src/utils/action-metadata.ts	Updated relative imports to include .js extensions
languageserver/src/utils/action-metadata.test.ts	Updated relative imports to include .js extensions
languageserver/src/on-completion.ts	Updated relative imports to include .js extensions
languageserver/src/index.ts	Updated relative imports to include .js extensions
languageserver/src/file-provider.ts	Updated relative imports to include .js extensions
languageserver/src/description-providers/action-input.ts	Updated relative imports to include .js extensions
languageserver/src/description-providers/action-input.test.ts	Updated relative imports to include .js extensions
languageserver/src/description-providers/action-description.ts	Updated relative imports to include .js extensions
languageserver/src/description-providers/action-description.test.ts	Updated relative imports to include .js extensions
languageserver/src/description-provider.ts	Updated relative imports to include .js extensions
languageserver/src/context-providers/variables.ts	Updated relative imports to include .js extensions
languageserver/src/context-providers/steps.ts	Updated relative imports to include .js extensions
languageserver/src/context-providers/steps.test.ts	Updated relative imports to include .js extensions
languageserver/src/context-providers/secrets.ts	Updated relative imports to include .js extensions
languageserver/src/context-providers/action-outputs.ts	Updated relative imports to include .js extensions
languageserver/src/context-providers.ts	Updated relative imports to include .js extensions
languageserver/src/context-providers.test.ts	Updated relative imports to include .js extensions
languageserver/src/connection.ts	Updated relative imports to include .js extensions
docs/esm-migration-plan.md	Updated migration status, added TL;DR section, documented skipLibCheck requirement, and updated completion status for languageserver package

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