feat: patch missing context and SourceCode methods for v10

[Pixel998]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

ESLint v10 will remove several methods from the context and SourceCode objects:

From context:

• parserOptions → use context.languageOptions.parserOptions
• getCwd() → use context.cwd
• getFilename() → use context.filename
• getPhysicalFilename() → use context.physicalFilename
• getSourceCode() → use context.sourceCode

From SourceCode:

• getTokenOrCommentBefore() → use getTokenBefore({ includeComments: true })
• getTokenOrCommentAfter() → use getTokenAfter({ includeComments: true })
• isSpaceBetweenTokens() → use isSpaceBetween()
• getJSDocComment() → removed entirely (no direct replacement)

This change patches those methods to maintain backward compatibility so existing ESLint v9 rules and plugins continue to work with @eslint/compat.

What changes did you make? (Give an overview)

• Added compatibility patches in fixupRule() to restore these methods when missing.
• Updated fixupPluginRules() and fixupConfigRules() to wrap affected rules automatically.
• Added tests verifying parity with ESLint v9 behavior for each patched method.

Related Issues

Fixes #279

Is there anything you'd like reviewers to focus on?

[mdjermanovic]

Can we also patch context.parserOptions?

[Copilot]

Pull Request Overview

This PR updates the @eslint/compat package to adapt ESLint v9.x rules/plugins for use in ESLint v10.x. The main changes involve rewriting the compatibility layer to restore deprecated context and sourceCode methods using a Proxy-based approach instead of wrapping visitor methods.

• Replaces the visitor-wrapping approach with a Proxy-based context wrapper
• Restores deprecated context methods (getCwd, getFilename, getPhysicalFilename, getSourceCode) and sourceCode methods (getTokenOrCommentBefore/After, isSpaceBetweenTokens, getJSDocComment)
• Updates documentation to reflect ESLint v9.x → v10.x compatibility (previously v8.x → v9.x)

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/compat/src/fixup-rules.js	Implements new Proxy-based compatibility layer for context and sourceCode objects, replacing the previous visitor-wrapping approach
packages/compat/tests/fixup-rules.test.js	Updates test suite to verify restoration of deprecated methods, replacing legacy schema and method compatibility tests
packages/compat/README.md	Updates documentation to reference ESLint v9.x → v10.x compatibility instead of v8.x → v9.x

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[mdjermanovic]

LGTM, thanks!

The tests will really be checking the new features only when we update ESLint to v10 in this repo, but I verified manually that they are passing and that generally everything works well when the methods/properties this PR patches are removed from ESLint.

Since this is a feature, it needs a second review before merging.

[nzakas]

LGTM. Thanks.