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.

pkgs/nomarchy-install/patch-template.py

@@ -57,6 +57,17 @@ def patch_flake(text: str, v: dict) -> str:
         f'username = "{nix_str(v["username"])}"; # <- your login name',
         "flake username",
     )
+    # ISO build bakes the ref it was built from (main vs v1). Must match the
+    # option surface the installer writes into system.nix (#124).
+    if v.get("flakeUrl"):
+        text, n = re.subn(
+            r'inputs\.nomarchy\.url = "[^"]*";',
+            f'inputs.nomarchy.url = "{nix_str(v["flakeUrl"])}";',
+            text,
+            count=1,
+        )
+        if n != 1:
+            sys.exit("patch-template: could not patch inputs.nomarchy.url")
     profiles = v.get("hardwareProfiles") or []
     if profiles:
         items = " ".join(f'"{nix_str(p)}"' for p in profiles)