test(install): drop the dead bzip2-less tar stub from the Get-PinnedGit E2E

Get-PinnedGit no longer invokes tar at all (no $inboxTar seam exists since
the PortableGit pin), so the C# stub tar.exe and the Invoke-Native override
that bound it were never reached: the test compiled a stub for nothing and
its docstring described a mechanism the installer does not have. Keep the
real-download Get-PinnedGit run under a bzip2-less PATH and the git.exe +
bash.exe contract checks; that is what the test proves.

tests/scripts/install/test_install_ps1_pinned_git_extract.py

@@ -1,19 +1,14 @@
-"""Pinned git staging must not need a bzip2-capable tar (#122512).
+"""Pinned git staging must not need a bzip2-capable tar (#122512, #122774).
 
-The reported Windows 10 box has no bzip2.exe on PATH, and its System32
-tar.exe cannot run the bzip2 filter
-("tar.exe: Error opening archive: Can't initialize filter; unable to run
-program \"bzip2 -d\""), so extracting the pinned .tar.bz2 fails and
-bootstrap dies at stage=prerequisites with "failed to extract pinned git
-archive".
-
-The driver below reproduces that machine deterministically: PATH carries
-no bzip2, and the installer's own Invoke-Native seam resolves $inboxTar
-to a stub System32 tar.exe that only prints the reported error. Then it
-runs the real Get-PinnedGit against the real pinned archive and demands
-a working git.exe plus the bundled bash contract pm/shell.py relies on.
+Stock Windows 10 ships a System32 tar.exe without a bzip2 filter, so the
+old .tar.bz2 pin died at stage=prerequisites ("tar.exe: Error opening
+archive: Can't initialize filter; unable to run program \"bzip2 -d\"").
+Get-PinnedGit now stages the PortableGit self-extractor, which needs
+neither tar nor bzip2. The driver below runs the real Get-PinnedGit
+against the real pinned archive with a PATH that carries no bzip2 (or
+anything else to fall back on) and demands a working git.exe plus the
+bundled bash contract pm/shell.py relies on.
 """
-import os
 import subprocess
 import textwrap
 from pathlib import Path
@@ -22,34 +17,10 @@ import pytest
 
 ROOT = Path(__file__).resolve().parents[3]
 INSTALLER = ROOT / "scripts" / "install.ps1"
-CSC = (
-    Path(os.environ.get("SystemRoot", r"C:\Windows"))
-    / "Microsoft.NET" / "Framework64" / "v4.0.30319" / "csc.exe"
-)
 
 
 @pytest.mark.platforms("windows")
 def test_pinned_git_extracts_without_a_bzip2_capable_tar(tmp_path):
-    assert CSC.is_file(), f"missing C# compiler: {CSC}"
-
-    # The reporter's System32 tar.exe: it exists, but has no bzip2 filter.
-    stub_src = tmp_path / "bzip2less_tar.cs"
-    stub_src.write_text(
-        "using System; class Stub { static int Main(string[] a) { "
-        'System.Console.Error.WriteLine("tar.exe: Error opening archive: '
-        "Can't initialize filter; unable to run program \\\"bzip2 -d\\\"\"); "
-        "return 1; } }",
-        encoding="ascii",
-    )
-    fake_root = tmp_path / "sysroot"
-    stub_tar = fake_root / "System32" / "tar.exe"
-    stub_tar.parent.mkdir(parents=True)
-    compiled = subprocess.run(
-        [str(CSC), "/nologo", f"/out:{stub_tar}", str(stub_src)],
-        capture_output=True, text=True, timeout=120,
-    )
-    assert compiled.returncode == 0, compiled.stdout + compiled.stderr
-
     driver = tmp_path / "driver.ps1"
     driver.write_text(
         textwrap.dedent(f"""
@@ -57,13 +28,6 @@ def test_pinned_git_extracts_without_a_bzip2_capable_tar(tmp_path):
             $env:HERMES_RUNTIME_DIR = '{tmp_path / "tools"}'
             # This machine has no bzip2 (and nothing else to fall back on).
             $env:PATH = "$env:SystemRoot\\System32;$env:SystemRoot"
-            function Invoke-Native {{
-                param([scriptblock]$Command)
-                # Dynamic scope: bind the installer's $inboxTar to the
-                # bzip2-less stub before running its extraction command.
-                $inboxTar = '{stub_tar}'
-                & $Command
-            }}
             $git = Get-PinnedGit
             if (-not $git) {{ exit 9 }}
             & $git --version 2>$null | Out-Null