Implement reportStyleChecksAsWarnings

[jakebailey]

This implements typescript.reportStyleChecksAsWarnings, which defaults to true (like VS Code). It converts a select number of diagnostics in the editor from errors to warnings. This allows for F8 to skip to errors and not dead code, which is sometimes desirable.

We have to implement this server side, lest we insert more hacks in the VS Code client which I really would prefer not to do.

The place we have to do this is sort of icky, but will probably become less weird in the future when we stick prefs into the context like caps.

[Copilot]

Pull Request Overview

This PR implements the reportStyleCheckAsWarnings user preference, which defaults to true (matching VS Code behavior). When enabled, specific style-related diagnostics (unreachable code, unused declarations, etc.) are converted from errors to warnings in the editor, allowing F8 navigation to skip over them and focus on actual errors.

Key changes:

• Added ReportStyleCheckAsWarnings field to UserPreferences with proper parsing and default value
• Modified diagnostic conversion to downgrade specific error codes to warnings when the setting is enabled
• Updated test helper to properly identify suggestion diagnostics (excluding warnings with tags)

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/ls/lsutil/userpreferences.go	Added ReportStyleCheckAsWarnings preference with default value true
internal/ls/lsconv/converters.go	Implemented diagnostic severity conversion logic and defined style check diagnostic codes
internal/ls/diagnostics.go	Integrated reportStyleCheckAsWarnings parameter into pull diagnostics
internal/fourslash/fourslash.go	Fixed isSuggestionDiagnostic to only check severity, not tags
internal/fourslash/tests/unreachableCodeDiagnostics_test.go	Added test for unreachable code warnings
testdata/baselines/reference/fourslash/syntaxandSemanticDiagnostics/unreachableCodeDiagnostics.baseline	Expected baseline showing unreachable code as warning

[Copilot]

The DiagnosticToLSPPush function is missing the reportStyleCheckAsWarnings parameter and doesn't pass it to diagnosticOptions. This means push diagnostics (used for textDocument/publishDiagnostics in session.go) won't respect the user preference to convert style checks to warnings. The function signature should accept a reportStyleCheckAsWarnings bool parameter like DiagnosticToLSPPull does, and pass it to diagnosticOptions.

[jakebailey]

Push diags are only used for program diags which these cannot be; but this will gain the functionality through context at some point, yes

[jakebailey]

I made a typo because I copied VS Code's typo instead of copying the actual name of the setting...