Fix listFiles/listFilesOnly

[jakebailey]

Fixes #963

I redid this function, copying the structure of emitFilesAndReportErrors from Strada. This now matches in behavior and --listFiles/--listFilesOnly now work.

[Copilot]

Pull Request Overview

This PR refactors file emission to use a unified emitFilesAndReportErrors workflow and ensures --listFiles/--listFilesOnly flags produce the expected output.

• Replaced calls to compileAndEmit with emitFilesAndReportErrors in watcher and CLI paths.
• Copied and adapted emission logic from Strada into tsc.go, including diagnostic collection and timing.
• Added a new listFiles helper to output source file names when requested.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
internal/execute/watcher.go	Swapped compileAndEmit for emitFilesAndReportErrors
internal/execute/tsc.go	Replaced emission function, updated diagnostics flow, added listFiles and imported slices

Comments suppressed due to low confidence (2)

internal/execute/tsc.go:328

• Add unit tests for listFiles to verify correct behavior under both --listFiles and --listFilesOnly flags, ensuring coverage of the new listing functionality.

func listFiles(sys System, program *compiler.Program) {

internal/execute/tsc.go:276

• [nitpick] Consider implementing declaration diagnostics or removing this placeholder comment to keep the codebase clean and maintainable.

// !!! GetDeclarationDiagnostics