fix(installer): harden the lock path against the AMD-iGPU DPMS lockout

An idle lock on this Strix Halo box wedged the whole session: hyprlock died and the compositor stayed locked with no prompt, recoverable only from a console. It's a documented AMD-integrated-Radeon failure (hyprlock#953, Hyprland#5822) -- a display power cycle via DPMS invalidates the GPU resources the lock client holds, so hyprlock loses its surface and exits without unlocking. No coredump, no OOM; the GPU pulls the rug out.

Two installer changes, both scoped and tested:

update_grub_cmdline adds amdgpu.runpm=0 on AMD machines only. Disabling GPU runtime power management keeps those resources valid across a display cycle -- the root fix. A no-op on Intel/NVIDIA, and it rides the existing merge so no boot-critical token is touched.

configure_hyprlock_pam writes a complete PAM stack. The hyprlock package ships only `auth include login`, leaving account and session uninitialised so pam_end() crashes on cleanup -- a separate documented lockout cause. All three phases now resolve through login, inheriting the keyring the graphical login uses.

CALL_SITES pins both new wirings. 372 unit tests, exit 0; each addition proven by reverting it.

1 files changed, 85 insertions, 0 deletions

diff --git a/tests/installer-steps/test_hyprlock_pam.py b/tests/installer-steps/test_hyprlock_pam.py
new file mode 100644
index 0000000..8d7295f
--- /dev/null
+++ b/tests/installer-steps/test_hyprlock_pam.py
@@ -0,0 +1,85 @@
+"""Tests for configure_hyprlock_pam in the archsetup installer.
+
+hyprlock's packaged /etc/pam.d/hyprlock ships only `auth include login`, with no
+account or session sections. pam_end() then crashes cleaning up handles that
+were never initialised -- one of the documented causes of the hyprlock lockout
+where the session wedges with no prompt (hyprlock#953). configure_hyprlock_pam
+writes a complete stack so the account and session phases run.
+
+These tests exercise the REAL function body, extracted from the `archsetup`
+script at run time, against a fixture PAM path.
+
+Run from repo root:
+    python3 -m unittest tests.installer-steps.test_hyprlock_pam
+"""
+
+import os
+import subprocess
+import tempfile
+import unittest
+
+REPO_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+ARCHSETUP = os.path.join(REPO_ROOT, "archsetup")
+
+
+def run(path):
+    script = (
+        'logfile=/dev/null\n'
+        'display() { :; }\n'
+        'backup_system_file() { :; }\n'
+        'error_warn() { echo "WARN:$1"; return 1; }\n'
+        "source <(sed -n '/^configure_hyprlock_pam() {/,/^}/p' \"%s\")\n"
+        'configure_hyprlock_pam "%s"\n'
+    ) % (ARCHSETUP, path)
+    return subprocess.run(["bash", "-c", script], capture_output=True,
+                          text=True, timeout=10)
+
+
+class ConfigureHyprlockPam(unittest.TestCase):
+    def _write(self, initial="auth include login\n"):
+        fd, path = tempfile.mkstemp(prefix="pam-hyprlock-")
+        os.close(fd)
+        with open(path, "w") as f:
+            f.write(initial)
+        self.addCleanup(os.remove, path)
+        return path
+
+    def _stack(self, path):
+        with open(path) as f:
+            return [l.split()[0] for l in f if l.strip()
+                    and not l.lstrip().startswith("#")]
+
+    # ---------------------------------------------------------- normal ----
+    def test_writes_all_three_phases(self):
+        path = self._write()
+        run(path)
+        phases = set(self._stack(path))
+        self.assertEqual(phases, {"auth", "account", "session"},
+                         "the complete stack must carry all three PAM phases")
+
+    def test_account_and_session_are_the_added_ones(self):
+        path = self._write()
+        run(path)
+        stack = self._stack(path)
+        self.assertIn("account", stack)
+        self.assertIn("session", stack)
+
+    # -------------------------------------------------------- boundary ----
+    def test_idempotent_on_rerun(self):
+        path = self._write()
+        run(path)
+        first = open(path).read()
+        run(path)
+        self.assertEqual(open(path).read(), first,
+                         "a second run must not stack duplicate lines")
+
+    def test_overwrites_the_incomplete_package_default(self):
+        # The package default is exactly `auth include login`; a re-run replaces
+        # it wholesale rather than appending to it.
+        path = self._write("auth include login\n")
+        run(path)
+        self.assertEqual(self._stack(path).count("auth"), 1)
+
+
+if __name__ == "__main__":
+    unittest.main()