fix(install): bake dconf, seed main, name ISO, display modes (#123–#126)

Batch of existing-bug fixes from Acer/XPS install findings:

- #123: HM pre-activate creates /run/user/$UID and prefers
  dbus-run-session so dconf no longer aborts the desktop bake
- #124: main-built ISOs seed ?ref=main; patch-template rewrites
  inputs.nomarchy.url from NOMARCHY_FLAKE_URL (was set but unused)
- #125: image.baseName → nomarchy-live-….iso (not nixos-live-…)
- #126: Display mode list sorted by pixel area; toast shows hyprctl
  size; TESTING notes QEMU fixed-window scaling illusion

Verified: V0 flake check, installer-safety, baseName eval, patch-template
flakeUrl rewrite, mode-sort fixture.

docs/TESTING.md

@@ -122,6 +122,11 @@ Hyprland's headless backend otherwise aborts in a VM-only zero-output state.
   script's qemu flags; on real hardware check `journalctl -b -u greetd`.
 - **Tiny resolution**: the live config forces `monitor = ,highres,auto,1`;
   if QEMU still picks 1024×768, resize the window — Hyprland follows.
+- **Display menu + QEMU**: System › Display mode list is sorted by **pixel
+  area** (highest first). After a pick, the toast shows hyprctl’s reported
+  size. In a **fixed-size** QEMU/viewer window, a higher guest mode still
+  *looks* smaller (more pixels in the same window) — that is viewer scaling,
+  not an inverted apply. Trust hyprctl / the toast numbers.
 - **First theme switch is the slowest**: it evaluates the flake on a RAM
   disk. Subsequent switches reuse the eval cache.