fix(unsaved): rework logic for inferring filetype for unsaved documents

[isbecker]

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[Copilot]

Pull request overview

This PR reworks the logic for inferring file types for unsaved documents in the VSCode treefmt extension. The main changes include refactoring the getExtensionForLanguage function to better handle language extension detection, extracting testable logic into separate functions, migrating from .eslintrc.json to ESLint flat config (eslint.config.mjs), adding comprehensive test coverage for the new logic, and upgrading dependencies.

• Improved stdin specifier inference for unsaved documents by preferring actual file extensions over bare filenames
• Refactored configuration loading logic into testable units
• Added comprehensive test suite with new test files and helpers

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/treefmtUtils.ts	Refactored filetype inference logic, extracted helper functions, added test exports
src/test/testContext.ts	New helper for creating test context with mock extension context
src/test/stdinTokenInference.test.ts	New tests for stdin token inference logic
src/test/pathAndExtensionHelpers.test.ts	New tests for path and extension helper functions
src/test/extension.test.ts	Reorganized test suite to use modular test registration
src/test/environment.test.ts	New tests for environment validation
src/test/commands.test.ts	New tests for command execution
src/test/commandResolution.test.ts	New tests for command resolution logic
eslint.config.mjs	Migration to ESLint v9 flat config (with issues)
.github/workflows/test.yaml	New CI workflow for running tests
.eslintrc.json	Removed legacy ESLint configuration
package.json	Updated dependencies and version bump
package-lock.json	Dependency updates

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