hermes_cli.runtime_paths (venv generations, selection, activation) moves to
pm.environments, and gains venv_bin_dir / venv_python / project_python. Every
in-tree caller asks pm for an interpreter now; pm no longer reaches back into
hermes_cli for its own environment layout (pm.packages, pm.extras, pm.ensure,
pm.paths imported hermes_cli.runtime_paths). The three open-coded
"Scripts/python.exe or bin/python" ladders in pm collapse onto venv_python.
hermes_constants.venv_python_path / venv_bin_dir and hermes_cli.runtime_paths
stay as frozen-updater-surface shims only (tests/compat/old_updater_surface.json).
To keep the boot path light, pm/__init__ resolves its facade lazily (PEP 562)
and pm.registry loads the built-in package definitions on first read instead of
at import: `import hermes_bootstrap` now loads pm + pm.environments only (25ms,
was 37ms with the eager facade dragging in the downloader). The stripped-payload
fixtures that ship only pre-import files keep working for the same reason.
Also restores two frozen-surface re-exports the F401 sweep dropped
(banner._github_compare_behind, cua_backend.resolve_cua_driver_cmd).
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