feat(suspend): re-enable suspend on s2idle, drop diagnostic scaffolding

Confirmed root cause: this hardware's S3 (deep) firmware path triggers a
fatal wake-from-suspend hang only on linux-hardened. INIT_ON_FREE + slab
hardening + tighter locking turn a latent driver race that stock linux
gets away with into an unrecoverable panic so early the journal isn't
even flushed. mem_sleep_default=s2idle bypasses the BIOS S3 path
entirely (s0ix is a pure-kernel low-power state) and suspends/resumes
reliably under hardened.

This is a widespread Lenovo S3 firmware issue across post-2018
ThinkPads (see Ubuntu T560, X1C9/10/11 reports). Lenovo themselves
moved newer firmwares to s2idle-only. Not a linux-hardened bug per se;
just hardened being a strict enough kernel to make the bug fatal.

Keep:
* mem_sleep_default=s2idle in etc/kernel/cmdline-linux-hardened.tmpl
  (only the hardened UKI; stock linux keeps unchanged shared cmdline)

Revert (all the diagnostic / speculative scaffolding from the last
few commits):
* MODULES=(intel_lpss_pci) → MODULES=()  — Arch wiki touchpad fix was
  not the cause here
* nmi_watchdog=panic softlockup_panic=1 panic=10 — only needed to
  auto-reboot during diagnosis
* no_console_suspend — diagnostic-only
* etc/systemd/logind.conf.d/20-no-suspend.conf  — masking workaround
* sleep-target masking block in run_onchange_after_deploy-etc.sh.tmpl,
  replaced with a one-shot cleanup that removes any leftover
  /dev/null symlinks from systems that ran the previous version
* systemd-pstore.service from systemd-units/system.txt — added only to
  catch the diagnostic panic
* diagnose-suspend.sh helper (and its .gitignore/.chezmoiignore entries)
* sway suspend → lock-session keybind workaround
* power-menu.sh Suspend entry restoration
* KEYBINDS.md docs

1 files changed, 6 insertions, 4 deletions

diff --git a/etc/mkinitcpio.d/linux-hardened.preset b/etc/mkinitcpio.d/linux-hardened.preset
index 90be917..fcb94a5 100644
--- a/etc/mkinitcpio.d/linux-hardened.preset
+++ b/etc/mkinitcpio.d/linux-hardened.preset
@@ -1,9 +1,11 @@
 # mkinitcpio preset for the 'linux-hardened' kernel. Produces a UKI at
 # /boot/EFI/Linux/arch-linux-hardened.efi alongside the stock linux UKI.
-# Uses its own cmdline file (etc/kernel/cmdline-linux-hardened.tmpl)
-# carrying hang-detection knobs while we validate the suspend/resume
-# fix on this hardware. The stock linux UKI keeps the minimal
-# etc/kernel/cmdline.tmpl. Register the EFI entry once with efibootmgr:
+# Uses its own cmdline file (etc/kernel/cmdline-linux-hardened.tmpl) to
+# force `mem_sleep_default=s2idle`: this hardware's S3 firmware path
+# wakes reliably on stock linux but hard-hangs the hardened kernel
+# (INIT_ON_FREE + slab hardening turn a latent driver race fatal).
+# Stock linux keeps the minimal etc/kernel/cmdline.tmpl. Register the
+# EFI entry once with efibootmgr:
 #
 #   sudo efibootmgr --create --disk /dev/nvme0n1 --part 1 \
 #     --label 'Arch Hardened' --loader '\EFI\Linux\arch-linux-hardened.efi'