zen: switch from twilight nightly to stable channel

twilight re-publishes under the same 1.22t tag, so the pinned hash goes
stale and `nh home switch` fails with a fixed-output hash mismatch. Move
to the stable `default` package (branded zen-beta, 1.21.5b), which uses
proper versioned releases.

- zen-browser.nix: twilight-official -> default
- xdg.nix: zen-twilight.desktop -> zen-beta.desktop mimeapp defaults
- flake.lock: bump zen-browser input

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

flake.lock

@@ -232,11 +232,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1781497404,
-        "narHash": "sha256-9GAF8sSsnkyCVCWkomXR0T+zdSxyUlfPt6neQidimdg=",
+        "lastModified": 1782839684,
+        "narHash": "sha256-vzs4SBgPsK4aNzlJR2PpFwtARazXMOxZonQnDz0YHxk=",
         "owner": "nix-community",
         "repo": "home-manager",
-        "rev": "1285cd3d6882a9847f2d56ed5541b3350c8a6162",
+        "rev": "2a37d71bbe69e1522ddabf03a4cea0374958bdbe",
         "type": "github"
       },
       "original": {
@@ -1091,11 +1091,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1782623843,
-        "narHash": "sha256-zQdTvI8jcVfblsrWafw1ykTnCVoV94ttxb5e6drwVaI=",
+        "lastModified": 1783190846,
+        "narHash": "sha256-UcdKHKcDxLxBon0HsOjDRRA7l1vVT28R83LkCIAlYYc=",
         "owner": "0xc000022070",
         "repo": "zen-browser-flake",
-        "rev": "c59e57b9c6ea4c86f9f3b7efc92db3cbd305d078",
+        "rev": "0758bc86f7a55bbe002f0cede9e1a49e5a6e34d9",
         "type": "github"
       },
       "original": {

home/common/features/xdg.nix

@@ -20,11 +20,11 @@ _:
       enable = true;
       defaultApplications = {
         # web
-        "text/html" = "zen-twilight.desktop";
-        "x-scheme-handler/http" = "zen-twilight.desktop";
-        "x-scheme-handler/https" = "zen-twilight.desktop";
-        "x-scheme-handler/avbout" = "zen-twilight.desktop";
-        "x-scheme-handler/unknown" = "zen-twilight.desktop";
+        "text/html" = "zen-beta.desktop";
+        "x-scheme-handler/http" = "zen-beta.desktop";
+        "x-scheme-handler/https" = "zen-beta.desktop";
+        "x-scheme-handler/avbout" = "zen-beta.desktop";
+        "x-scheme-handler/unknown" = "zen-beta.desktop";
 
         # video
         "video/mp4" = "mpv.desktop";

home/common/programs/zen-browser.nix

@@ -1,4 +1,6 @@
 { inputs, pkgs, ... }:
 {
-  home.packages = [ inputs.zen-browser.packages.${pkgs.stdenv.hostPlatform.system}.twilight-official ];
+  # `default` is Zen's stable channel (branded "zen-beta", binary/desktop `zen-beta`).
+  # Avoids twilight's recurring hash-mismatch breakage (nightly re-tags under the same version).
+  home.packages = [ inputs.zen-browser.packages.${pkgs.stdenv.hostPlatform.system}.default ];
 }