feat: add automatic updates for vibetyper, msty-studio, zellij-ps

- vibetyper/msty-studio: unversioned AppImage URLs → HEAD/Last-Modified
  check via custom update.sh, refreshes sha256 when upstream binary changes
- zellij-ps: switch to branch-tracking (master tip via Gitea API) since
  helper-scripts repo has no tags
- all three expose passthru.updateScript so the existing CI workflow
  discovers them via is_custom_update_script

pkgs/vibetyper/default.nix

@@ -1,3 +1,4 @@
+# last-modified: Fri, 24 Jul 2026 10:50:57 GMT
 {
   appimageTools,
   fetchurl,
@@ -6,6 +7,8 @@
 }: let
   pname = "vibetyper";
   version = "1.4.0";
+  # Upstream publishes to an unversioned URL — ./update.sh watches Last-Modified
+  # and refreshes the sha256 when the binary changes. Bump `version` manually.
   src = fetchurl {
     url = "https://cdn.vibetyper.com/releases/linux/VibeTyper.AppImage";
     sha256 = "sha256-p4MOTKbEMIUhwhyGSE/l6ucwpPjeTELJ0lX4TXrKf2Y=";
@@ -29,6 +32,8 @@ in
               --set VIBE_DISABLE_HYPRLAND_INDICATOR_NO_BLUR 1
     '';
 
+    passthru.updateScript = ./update.sh;
+
     meta = {
       description = "VibeTyper - AI-powered typing assistant";
       homepage = "https://vibetyper.com";

pkgs/vibetyper/update.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env nix-shell
+#!nix-shell --pure -i bash -p bash curl nix nix-prefetch cacert git
+set -euo pipefail
+
+# Update vibetyper AppImage hash.
+#
+# Upstream publishes to an unversioned URL (VibeTyper.AppImage) — there is no
+# version-pinned URL and no usable GitHub release. To still catch updates, we:
+#   1. HEAD the URL and read the Last-Modified header
+#   2. Compare to the value stored as a `# last-modified:` comment in default.nix
+#   3. If changed: re-download, compute sha256, update hash + comment, commit
+#
+# The version attribute stays static (manual bump) — only the binary hash is
+# refreshed automatically.
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+NIX_FILE="$SCRIPT_DIR/default.nix"
+URL="https://cdn.vibetyper.com/releases/linux/VibeTyper.AppImage"
+
+echo "Checking $URL ..."
+# -f: fail on HTTP errors, -s: silent, -S: show errors, -I: HEAD, -L: follow redirects
+HEADERS=$(curl -fsSIL "$URL")
+NEW_LAST_MODIFIED=$(echo "$HEADERS" | tr -d '\r' \
+  | awk -F': ' 'tolower($1)=="last-modified" {print $2; exit}')
+
+if [[ -z "$NEW_LAST_MODIFIED" ]]; then
+  echo "ERROR: Could not read Last-Modified header from $URL" >&2
+  exit 1
+fi
+
+# Read stored Last-Modified from `# last-modified:` comment in the nix file
+CURRENT_LAST_MODIFIED=$(awk -F': ' '/^# last-modified:/ {sub(/^# last-modified: /, ""); print; exit}' "$NIX_FILE")
+
+echo "Current: ${CURRENT_LAST_MODIFIED:-<none>}"
+echo "Latest:  $NEW_LAST_MODIFIED"
+
+if [[ "$NEW_LAST_MODIFIED" == "$CURRENT_LAST_MODIFIED" ]]; then
+  echo "No change, nothing to do."
+  exit 0
+fi
+
+echo "==> Content changed, refreshing hash..."
+
+# Compute new sha256 (SRI form, matches existing `sha256 = "sha256-..."` style)
+HASH=$(nix-prefetch-url --type sha256 "$URL" 2>/dev/null)
+SRI=$(nix hash convert --hash-algo sha256 --to sri "$HASH")
+echo "New sha256: $SRI"
+
+# Update the sha256 attribute (keeps the existing `sha256 = "sha256-..."` shape)
+sed -i "s|^\([[:space:]]*\)sha256 = \"[^\"]*\";|\1sha256 = \"$SRI\";|" "$NIX_FILE"
+
+# Update or insert the last-modified marker comment
+if grep -q '^# last-modified:' "$NIX_FILE"; then
+  sed -i "s|^# last-modified:.*|# last-modified: $NEW_LAST_MODIFIED|" "$NIX_FILE"
+else
+  sed -i "1i # last-modified: $NEW_LAST_MODIFIED" "$NIX_FILE"
+fi
+
+echo "Updated $NIX_FILE"
+
+# Commit when inside a git repo
+NIXPKGS_ROOT=$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel 2>/dev/null || true)
+if [[ -n "$NIXPKGS_ROOT" ]] && \
+   [[ -n "$(git -C "$NIXPKGS_ROOT" status --porcelain "$NIX_FILE")" ]]; then
+  git -C "$NIXPKGS_ROOT" add "$NIX_FILE"
+  git -C "$NIXPKGS_ROOT" commit -m "vibetyper: refresh AppImage ($NEW_LAST_MODIFIED)"
+  echo "==> Committed"
+fi