fix(bootstrap): start the PM tree from a venv editable-installed before pm existed

An install editable-built from main maps only the top-level packages it
saw then (setuptools' flat-layout finder: no `pm`) and never puts the
checkout on sys.path. After moving that checkout to this tree, `hermes`
died in hermes_cli/__init__.py: `__version__` was evaluated at import
through pm.paths, before anything had put the root on sys.path.

Two layers of the same break:

- hermes_cli.__version__ is served lazily (PEP 562). Shipped updaters
  still get it from `from hermes_cli import __version__`; importing the
  package no longer needs pm or reads the stamp.
- hermes_bootstrap hardens the import path before its first Hermes
  import, not only on the legacy post-swap branch. Without that, its
  `from pm.environments import ...` raised ModuleNotFoundError, which
  hermes_cli.main swallows, so the launch silently skipped
  prepare_launch: no blessed-checkout adoption and no PM sync, and the
  tree ran on main's dependencies until it hit ruamel.

Reproduced with a real main editable venv swapped to this tree: exact
user traceback before; after, a stamp-less blessed checkout adopts, PM
syncs, relaunches, and the command answers. The new test drives both
imports through a pre-PM style finder and is red with either half
reverted.

hermes_bootstrap.py

@@ -349,12 +349,16 @@ def _legacy_post_swap_invocation(argv: list[str]) -> tuple[Path, list[str]] | No
     return Path(argv[marker + 1]), argv[1:marker]
 
 
+# Everything below imports Hermes packages, so the root goes on sys.path first. A venv
+# editable-installed from a pre-PM tree maps only the top-level packages it knew then:
+# without this, ``pm`` is unimportable and the launch silently skips PM adoption.
+harden_import_path(str(_root))
+
 _legacy_post_swap = _legacy_post_swap_invocation(sys.argv[1:])
 if _legacy_post_swap is not None:
     # This continuation exists precisely because the replacement tree may not
     # run under the old release's dependency graph. Take it over before PM
     # activation, launch preparation, or argparse imports any of that graph.
-    harden_import_path(str(_root))
     from hermes_cli.update_handoff import _continue_legacy_post_swap
 
     _handoff_path, _argv_tail = _legacy_post_swap

hermes_cli/__init__.py

@@ -4,25 +4,31 @@ import os
 import sys
 
 __release_date__ = "2026.9.21"
+# Declared for type checkers and the old-updater surface audit; served lazily by __getattr__.
+__version__: str
 
 
-def _stamped_version() -> str:
+def __getattr__(name: str) -> str:
     """Old-updater compat: shipped updaters import ``__version__`` after the checkout swap.
 
     tests/compat/old_updater_surface.json freezes that import. In-tree code resolves
     identity through hermes_cli.version_info.get_version_info(); this reads only the
-    install stamp -- never git, since it runs on every import -- and keeps the
-    pre-stamp placeholder when a checkout has no stamp.
+    install stamp -- never git -- and keeps the pre-stamp placeholder when a checkout
+    has no stamp.
+
+    Lazy because ``pm`` is not importable when this package loads: a venv
+    editable-installed from a pre-PM tree maps only the top-level packages it knew
+    at install time, and the repo root reaches ``sys.path`` only once
+    ``hermes_bootstrap`` runs -- after this ``__init__``, from ``hermes_cli.main``.
     """
+    if name != "__version__":
+        raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
     from hermes_cli.steward import read_install_stamp
     from pm.paths import repo_root
 
     return str(read_install_stamp(repo_root()).get("baseVersion") or "0.0.0")
 
 
-__version__ = _stamped_version()
-
-
 def _ensure_utf8():
     """Force UTF-8 stdout/stderr to prevent UnicodeEncodeError crashes.
 

tests/test_hermes_bootstrap.py

@@ -229,6 +229,42 @@ else:
     assert result.stdout.strip() == "bootstrap-before-app"
 
 
+def test_pre_pm_editable_venv_reaches_pm_through_the_bootstrap(tmp_path):
+    """A venv editable-installed from a pre-PM tree must still start the PM-era tree.
+
+    setuptools' flat-layout editable finder maps only the top-level names it saw at
+    install time (no ``pm``) and never puts the checkout on ``sys.path``. The console
+    script imports ``hermes_cli`` first, then ``hermes_cli.main`` imports the bootstrap;
+    both must load, and the bootstrap must reach ``pm``, or PM adoption never runs.
+    """
+    root = Path(__file__).resolve().parents[1]
+    program = r"""
+import importlib.util, os, sys
+from importlib.abc import MetaPathFinder
+root = sys.argv[1]
+class PrePMEditableFinder(MetaPathFinder):
+    def find_spec(self, name, path=None, target=None):
+        if name == 'hermes_cli':
+            pkg = os.path.join(root, 'hermes_cli')
+            return importlib.util.spec_from_file_location(
+                name, os.path.join(pkg, '__init__.py'), submodule_search_locations=[pkg])
+        if name == 'hermes_bootstrap':
+            return importlib.util.spec_from_file_location(name, os.path.join(root, 'hermes_bootstrap.py'))
+        return None
+sys.meta_path.append(PrePMEditableFinder())
+sys.argv = ['hermes', 'pm', 'repair']
+import hermes_cli
+import hermes_bootstrap
+assert hermes_bootstrap._pm_repair is True
+print('reached-pm')
+"""
+    result = subprocess.run([sys.executable, "-I", "-S", "-c", program, str(root)],
+                            cwd=tmp_path, env={**os.environ, "HERMES_HOME": str(tmp_path / "home")},
+                            capture_output=True, text=True, timeout=30)
+    assert result.returncode == 0, result.stderr
+    assert result.stdout.strip() == "reached-pm"
+
+
 class TestHardenImportPath:
     """harden_import_path() must keep a same-named package in the launch
     directory from shadowing Hermes's own top-level modules — covering both