fix(install): resolve uv shims before salvage and validate the copy in place

Install-Uv accepted any file at $HermesHome\bin\uv.exe, and copied whatever
`Get-Command uv` returned into that location. Chocolatey's bin\uv.exe is a
ShimGen launcher that locates ..\lib\uv\tools\uv.exe RELATIVE to itself, so
the copy is dead on arrival; `& exe --version` does not throw on a nonzero
exit, so the launcher passed the try/catch and the Python stage then failed
with "Python 3.11 not available" (#110350). The re-run path trusted the same
broken copy again.

Building on KoNit-K's Test-ManagedUvBinary and its three call sites:

- Test-ManagedUvBinary merges stderr, relaxes the error preference, and
  returns the `uv <version>` line only on exit 0 -- a launcher's error text
  can no longer surface as "Managed uv found (Cannot find file ...)".
- Resolve-UvShimTarget maps a candidate to the standalone binary before the
  copy: `<name>.shim` sidecar (Scoop), the Chocolatey bin\ -> lib\<pkg>\tools\
  layout, symlinks (winget Links\); other reparse points (WindowsApps
  app-execution aliases) have no copyable file and skip the salvage.
- The salvage rung validates the candidate where it lives, copies, then
  validates the COPY at its new location and removes it on failure, so the
  stage fails honestly instead of reporting success over a dead launcher.
- scripts/tests/test-install-ps1-uv-shim-validation.ps1 drives the real
  Install-Uv with compiled fake uv binaries (a working uv and a
  location-relative launcher) under stubbed installer rungs; wired into
  installer-tests.yml for pwsh 7 and Windows PowerShell 5.1.

Co-authored-by: joaomarcos <joaomarcosdias444@gmail.com>

.github/workflows/installer-tests.yml

@@ -44,3 +44,11 @@ jobs:
       - name: System Node and npm compatibility (Windows PowerShell 5.1)
         shell: powershell
         run: powershell -NoProfile -ExecutionPolicy Bypass -File scripts/tests/test-install-ps1-node-compatibility.ps1
+
+      - name: Managed uv acceptance rejects relocated shims (pwsh 7)
+        shell: pwsh
+        run: pwsh -NoProfile -ExecutionPolicy Bypass -File scripts/tests/test-install-ps1-uv-shim-validation.ps1
+
+      - name: Managed uv acceptance rejects relocated shims (Windows PowerShell 5.1)
+        shell: powershell
+        run: powershell -NoProfile -ExecutionPolicy Bypass -File scripts/tests/test-install-ps1-uv-shim-validation.ps1