Format options + fourslash testing + fix formatting bugs

[iisaduan]

Adds formatting options and links up the server's FormatCodeOptions with the formatting functions. Also adds in basic structure for js, javascript, ts, and typescript scoped settings, and redirects LanguageService.UserPreferences() to return the preferences for the active file.

Moves formatCodeSettings to lsutil

Formatting is now being tested in fourslash, although not all the commands are implemented due to non-formatting tests crashing on insertion. I've added a fourslashTest property to skip the check for those specific crashes, so that the rest of the test can proceed as normal. The flag(s) can easily be commented out if investigating these crashes.

Also fixes a formatting bug that was adding extra spaces after newlines.

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Fixes #2450

[Copilot]

Pull request overview

This PR adds formatting options support and integrates it with the language server, enables fourslash testing for formatting functionality, and fixes a formatting bug related to extra spaces after newlines.

Key changes:

• Adds FormatCodeSettings structure with comprehensive formatting options
• Refactors configuration management to support both TypeScript and JavaScript scoped settings
• Fixes scanner bug that was calculating end-of-line positions incorrectly
• Updates fourslash test infrastructure to support formatting tests
• Reduces baseline diffs showing improved formatting convergence with TypeScript

Reviewed changes

Copilot reviewed 283 out of 283 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/scanner/scanner.go	Fixed off-by-one error in GetECMAEndLinePosition to correctly calculate line endings
internal/project/configuration.go	New configuration structure supporting separate TypeScript/JavaScript preferences
internal/project/snapshot.go	Refactored to use pointer-based Config and removed embedded format options
internal/project/session.go	Updated to manage Config objects instead of bare UserPreferences
internal/ls/lsutil/formatcodeoptions.go	New comprehensive formatting options with parsing and default values
internal/ls/lsutil/userpreferences.go	Integrated FormatCodeSettings into UserPreferences structure
internal/ls/format.go	Updated to use new format options from UserPreferences
internal/lsp/server.go	Enhanced configuration request to support multiple scopes (typescript/ts/javascript/js)
Test files	Multiple fourslash tests updated to use new verification methods
Baseline files	Reduced diff files showing formatting convergence improvements

[jakebailey]

The actual section is ts/js, but we should just ignore those for now since we don't pull inferred project compiler options out of it yet.

[jakebailey]

I would still delete ts and js here, I don't think they are real?

[jakebailey]

I think Config is a bit too generic of a name, and it does seem like this should live in lsutil since it's basically just a way to encode two user preferences structs and that isn't project specific.

[iisaduan]

ServerConfig?

[jakebailey]

CombinedUserPreferences? AllUserPreferences? I didn't come up with a good name so I didn't suggest one before, which is not helpful 😄

My hope is that in a future change, this struct is immutable too (probably in a rebase of my PR), just to make this easier to work with

[iisaduan]

I had originally imagined that we would factor out the stuff configures server side preferences (stuff that would never need to be passed into LanguageService). There's also tsserverOptions in strada, I figured we'd have similar options here (or are they all just on Server already?

[jakebailey]

Maybe I'm totally missing something, but the only reference to tsserverOptions is in a comment in Corsa...