Document remaining neon customizations from shell history; fix zram loose ends

Persist vm.swappiness=100 in /etc/sysctl.d/99-zram.conf and delete the
unused /swapfile. New NEON-CUSTOMIZATIONS.md covers keyd, USB-C DP
modules, HWE-edge kernel, tmpfs /tmp and localepurge, r8152 DKMS
history, tailscale, and third-party repos/tools.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -153,5 +153,16 @@ the eMMC has no audio yet (not investigated).
 
 Disk swapfile replaced by an 8GiB zstd zram device via `zram-tools`
 (`/etc/default/zramswap`), set up 2026-03-05. Documented in **`ZRAM.md`**.
-Loose ends as of 2026-09-27: `vm.swappiness=100` was only set at runtime
-(back to 60), and the unused 512MiB `/swapfile` is still on disk.
+`vm.swappiness=100` is persisted in `/etc/sysctl.d/99-zram.conf`, and the
+old `/swapfile` was deleted (both 2026-09-27).
+
+## Other neon customizations
+
+See **`NEON-CUSTOMIZATIONS.md`** (reconstructed 2026-09-27 from shell
+history): keyd Chromebook keyboard remap (built from source,
+`/etc/keyd/default.conf`, internal keyboard only), USB-C DisplayPort
+via `/etc/modules-load.d/cros-video.conf` (`cros_ec_typec`,
+`typec_displayport`), `linux-generic-hwe-24.04-edge` (why it's on 7.x
+kernels) plus the 6.17 fallback, `/tmp` on tmpfs + localepurge to spare
+the USB-card root, the removed r8152 DKMS driver, disabled tailscaled,
+and third-party apt repos and hand-installed tools.