Plumb through TokenFlagsSingleQuote; use for auto import quote detection

[andrewbranch]

Fixes #1697

[Copilot]

Pull Request Overview

This PR implements proper plumbing of the TokenFlagsSingleQuote flag to enable auto-import quote detection. The changes allow the compiler and language server to detect and preserve the quote style used in existing imports when generating new import statements.

Key changes:

• Scanner now sets TokenFlagsSingleQuote when parsing single-quoted strings
• Language server detects quote preference from existing imports in the file
• Node builder uses this flag to maintain consistent quote style in generated code

Reviewed Changes

Copilot reviewed 48 out of 48 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/scanner/scanner.go	Added flag setting for single-quoted strings during scanning
internal/ls/utilities.go	Implemented quote preference detection from source files and string literals
internal/ls/autoimports.go	Plumbed quote preference through import generation
internal/ls/autoimportfixes.go	Applied quote preference to generated module specifiers
internal/checker/nodebuilderimpl.go	Updated all string literal creation to respect single-quote flags
internal/fourslash/tests/autoImportQuoteDetection_test.go	Added test verifying quote style preservation in auto-imports
Various baseline files	Updated test outputs reflecting correct quote style preservation

[jakebailey]

Oops...

[andrewbranch]

This wasn't a porting mistake; in Strada we didn’t have this token flag, and we (for some reason unknown to me) intentionally didn't set the single-quote boolean on StringLiteral from the parser. It only existed for synthesized nodes, which means we had to check the source text on parse nodes and the property on synthesized nodes. The way we're doing it now seems like a better design all around. 🤷

[jakebailey]

Ah, gotcha.

[jakebailey]

Darn, conflicts with the other LS settings PR.