win32(installer): Normalize PATH handling and fix uninstall filtering [needs testing]

[yugook]

⚠️ This PR updates PATH handling logic in the Windows installer.
Changes are verified with string-based tests (PowerShell), but I would appreciate further testing on real Windows setups.

Summary

Normalize PATH handling in the Windows installer (build/win32/code.iss) and fix uninstall filtering:

• Trim trailing separators when comparing (\ and /)
• Case-insensitive comparison
• Consider 8.3 short names (when available)
• Handle empty / semicolon-terminated PATH without producing malformed values

Why

• Avoid duplicate PATH entries when the existing entry has a trailing slash or is in 8.3 short form.
• Ensure uninstall removes VS Code’s PATH entry (both long and short forms).

How

• Add TrimTrailingSlash helper.
• NeedsAddToPath: explode PATH, normalize each segment, compare against long and short names.
• AddToPath: treat empty/absent PATH specially; respect trailing ;.
• Uninstall: normalize {app}\bin, compare against both long/short, rebuild PATH cleanly.

Before / After (examples)

• Before: PATH contains …;C:\Program Files\Microsoft VS Code\bin\ → installer adds …;C:\Program Files\Microsoft VS Code\bin (duplicate).
• After: no duplicate added.
• Before: PATH contains …;C:\PROGRA~1\MICROS~1\bin → uninstall sometimes leaves it behind.
• After: long/short both removed.

Verification

• Windows Sandbox, PowerShell dry-run (strings only; no system writes):
  • trailing slash present → NeedsAddToPath: False; RemoveFromPath: entry removed
  • 8.3 short present → NeedsAddToPath: False; RemoveFromPath: entry removed
  • empty PATH → AddToPath: C:\Program Files\Microsoft VS Code\bin
  • PATH ends with ; → no malformed value produced
    (Full installer tests can be run if preferred.)

Risk / Impact

Low: changes are isolated to installer script and guarded when 8.3 names are not available.

[yugook]

@microsoft-github-policy-service agree