fix: skip VS filesystem scan on macOS/Linux to prevent extension hang (#611)

[rajbos]

Problem

Fixes #611 (related: #493)

On macOS and Linux, the extension was hanging on startup from version 0.0.22 onwards. The last log entry before the hang was:

[1:19:57 PM] 📁 Crush: found 0 project(s) in projects.json

Root Cause

VisualStudioDataAccess._discoverFromFilesystem() performs a recursive filesystem scan of the user's home directory at depth 7, looking for .vs/copilot-chat/sessions/ paths (Visual Studio project directories).

On macOS and Linux, Visual Studio doesn't exist — .vs/ directories are never created. However, the scan still walked through all subdirectories of ~/ synchronously using readdirSync, which on a typical developer machine (with many workspaces and deeply nested project trees) caused the extension to appear completely frozen.

Fix

Add an early-exit guard at the top of _discoverFromFilesystem():

if (os.platform() !== 'win32') { return; }

Visual Studio is a Windows-only application (Visual Studio for Mac was discontinued). There are no .vs/ session directories to find on macOS or Linux, so the scan is skipped entirely on those platforms. The log-based discovery path (_discoverFromLogs) is unaffected — it already exits early when the %LOCALAPPDATA%\Temp\VSGitHubCopilotLogs directory doesn't exist.

Testing

• TypeScript compiles cleanly (tsc --noEmit — 0 errors)
• Extension bundles cleanly (node esbuild.js)
• On Windows: behaviour unchanged — full filesystem scan still runs