Fix tsconfig/jsconfig priority for JS files when both configs coexist in same directory

[Copilot]

When tsconfig.json and jsconfig.json coexist in the same directory, JS files were always falling through to the inferred project instead of being picked up by jsconfig.json. The ancestor config search in computeConfigFileName was skipping the entire starting directory, preventing discovery of a sibling jsconfig.json after tsconfig.json rejected the file.

Fix

Aligned computeConfigFileName with TSServer's forEachConfigFileLocation behavior:

• When searching for ancestor of tsconfig.json: skip tsconfig.json but still check jsconfig.json in the same directory
• When searching for ancestor of jsconfig.json: skip both (unchanged behavior)

// Before: single boolean skipped everything in the directory
skip := skipSearchInDirectoryOfFile

// After: granular skip per config type
skipTsconfig := skipSearchInDirectoryOfFile
skipJsconfig := skipSearchInDirectoryOfFile && !strings.HasSuffix(fileName, "/tsconfig.json")

Test

Added test verifying JS files route to jsconfig.json and TS files route to tsconfig.json when both configs exist in the same directory.

[Copilot]

Pull request overview

Fixes configured-project discovery so that when tsconfig.json and jsconfig.json coexist in the same directory, JavaScript files can still be correctly picked up by jsconfig.json (instead of falling through to the inferred project) after tsconfig.json is found but does not include the JS file.

Changes:

• Adjusted computeConfigFileName ancestor search to skip tsconfig.json but still consider a sibling jsconfig.json when the starting file is tsconfig.json.
• Added a session test asserting JS files route to the jsconfig.json project while TS files route to the tsconfig.json project when both configs exist.

Show a summary per file

File	Description
internal/project/configfileregistrybuilder.go	Refines per-config skipping behavior during ancestor config discovery to match TSServer behavior in mixed tsconfig/jsconfig directories.
internal/project/session_test.go	Adds regression test for JS-vs-TS default project selection when both configs exist side-by-side.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 1