Reapply #1951 and #1960 after bad merge

[jakebailey]

Re-applies #1951 and #1960 after being accidentally reverted in #1961.

[Copilot]

Pull Request Overview

This PR re-applies changes from #1951 and #1960 that were lost due to a bad merge. The changes primarily focus on fixing how JSDoc type tags handle optional parameters in JavaScript files, improving reference directive handling in the language service, and ensuring proper export handling for function overloads.

• Fix JSDoc function signatures to properly treat unannotated parameters as optional in JavaScript files
• Improve handling of reference directives in document highlights and find-all-references
• Fix export handling for JSDoc-annotated function overload signatures

Reviewed Changes

Copilot reviewed 41 out of 41 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
testdata/baselines/reference/**/*.diff	Updated test baselines reflecting correct treatment of optional parameters in JavaScript
internal/ls/findallreferences.go	Fixed reference directive handling to use proper range entries instead of node entries
internal/ls/documenthighlights.go	Removed unnecessary condition check when processing reference entries
internal/fourslash/tests/documentHighlightReferenceDirective_test.go	Added test coverage for reference directive highlighting
internal/checker/emitresolver.go	Fixed overload detection to exclude JSDoc-flagged declarations
internal/checker/checker.go	Enhanced signature detection for untyped JavaScript functions and fixed JSDoc type tag application
internal/ast/utilities.go	Exported IsMethodOrAccessor function for external use
internal/ast/ast.go	Added nil check for parent node in accessKind function