install.ps1: the existing bundled JDK is deleted before its replacement is known-good

[fupelaqu]

Found reviewing PR #232 (Windows JDK bootstrap). Verified against install.ps1 as merged.

What happens

Install-EmbeddedJdk removes the existing JDK before the replacement exists:

if (Test-Path $staging)          { Remove-Item -Recurse -Force $staging }
if (Test-Path $EMBEDDED_JDK_DIR) { Remove-Item -Recurse -Force $EMBEDDED_JDK_DIR }   # install.ps1:203
New-Item -ItemType Directory -Force -Path $staging | Out-Null

try {
    Expand-Archive -Path $zip -DestinationPath $staging -Force                        # install.ps1:207
    ...

If Expand-Archive throws, the catch writes an error and returns $null, Resolve-Java returns $false and the script exits 1 — with <Target>\jdk already deleted.

Consequence

A previously working installation is left with no JVM at all, and the failure that causes it is realistic rather than exotic: the unpack needs the 180 MB zip plus roughly 300 MB expanded plus the ~309 MB jar in the same tree, so running out of disk lands squarely in this window. The user's next REPL launch fails, and the installer that broke it is the one they will re-run to fix it (see the re-download issue).

Suggested fix

Stage, then swap: unpack into $staging, verify bin\java.exe exists, and only then remove $EMBEDDED_JDK_DIR and move the new tree into place. The move is already the last step — only the delete has to travel with it.

The $staging delete on the line above is fine as it is: that directory is scratch by construction.

[fupelaqu]

Same bootstrap path: #233 (never probed on re-run), #236 (orphaned jdk/ on failure). All three would be fixed by one pass over Install-EmbeddedJdk / Resolve-Java.