fix: report real command exit codes from the PowerShell prompt wrapper

[HelloThisWorld]

Problem

Every Command Timeline entry in 1.3.0-beta1 shows Succeeded, including commands that clearly failed (node src\broken.js, missing-path cmdlet errors). Failure marks can never appear.

Root cause

Enable-WinTermShellIntegration installs a prompt wrapper whose first statement is Get-Module -Name 'winTerm.Shell'. That statement succeeds and resets $? before Invoke-WinTermPrompt reads it, so Get-WinTermExitCode -LastSuccess $true short-circuits to 0 on every prompt. The 133;D mark therefore always reports exit code 0 and the timeline renders every finished command as Succeeded.

Fix

• The wrapper captures $? as its first statement and passes it into the module call: & $module { param($s) Invoke-WinTermPrompt -LastSuccess $s } $winTermLastSuccess.
• Invoke-WinTermPrompt gains an optional -LastSuccess parameter; when omitted it still reads $? at entry, preserving direct-invocation behavior.

Tests

scripts/winterm/test-shell-integration.ps1 gains Test-PowerShellPromptExitCodes, which enables integration and drives the installed global prompt function the same way the console host does:

• first prompt emits 133;A and no 133;D
• successful command → 133;D;0
• failed cmdlet (Get-Item on a missing path) → 133;D;1
• native failure (cmd /c exit 5) → 133;D;5
• success after a failure recovers to 133;D;0

Verified red on the unfixed module (fails with "A failed cmdlet was not reported as exit code 1.") and green with the fix. Full suite (WindowsPowerShell + PowerShell7 + CMD) passes, and the privacy gate passes.