fix: --update --tag dev pulls :dev-cli alias instead of guessing version

- When --tag dev/main is used and versioned image is missing locally,
  pull the branch alias (:dev-cli/:main-cli) which always exists
- This avoids pulling non-existent 0.0.0-lpb-dev-cli tags
- After first pull, subsequent --update uses versioned tags correctly

Author: localpibox

scripts/lpb.py

@@ -901,14 +901,18 @@ def cmd_update():
         images_to_update.append(web_img)
     if not images_to_update:
         # If a specific tag was requested, pull it even if not local
-        if cfg.image_tag and cfg.image_tag not in ("",):
-            if c.images_exists(CLI_IMAGE):
-                # Try to get the versioned image from remote
-                info(f"{cli_img} not found locally, pulling from remote...")
-                images_to_update.append(cli_img)
-                if c.images_exists(web_img):
-                    images_to_update.append(web_img)
-        if not images_to_update:
+        if cfg.image_tag and cfg.image_tag in ("dev", "main"):
+            # Use the branch alias tag (:dev-cli/:main-cli) which always exists
+            if cfg.image_tag == "dev":
+                alias_cli = f"{mod.CLI_IMAGE.rsplit(':', 1)[0]}:dev-cli"
+                alias_web = f"{mod.WEB_IMAGE.rsplit(':', 1)[0]}:dev-web"
+            else:
+                alias_cli = f"{mod.CLI_IMAGE.rsplit(':', 1)[0]}:main-cli"
+                alias_web = f"{mod.WEB_IMAGE.rsplit(':', 1)[0]}:main-web"
+            info(f"{cli_img} not found locally, pulling alias {alias_cli}...")
+            images_to_update.append(alias_cli)
+            images_to_update.append(alias_web)
+        elif not images_to_update:
             # Fall back to default images (no tag)
             for img in [CLI_IMAGE, WEB_IMAGE]:
                 if c.images_exists(img):