Setup searched for console scripts in a checkout-local venv that PM no
longer creates. Publish both commands through the shared writer after
PM setup, using store Python rather than a dependency interpreter.
Native and shell launchers load the selected dependency generation at
boot, retain the custom-home default, and ignore foreign Python paths.
Both installer stages reuse their bootstrap interpreter for publication.
PowerShell passes the resolved home to child processes.
Verified: 57 focused tests passed with one POSIX host skip. Real Windows
launchers, generated shell scripts, and both stage callers ran against
temporary trees. No full cold dependency install or native POSIX install
was run. The user-PATH edge is stubbed in the PowerShell test.
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