refactor: clean up image tag resolution — no legacy workarounds

- Read LPB_IMAGE_TAG env var at module level, set as default for cfg.image_tag
- Remove _resolve_image_tag() function
- Replace all cfg.image_tag or _resolve_image_tag() with just cfg.image_tag
- Clean separation: env var → default, --tag → override

Author: localpibox

scripts/lpb.py

@@ -134,6 +134,10 @@ def _load_stack_env() -> dict[str, str]:
 CLI_IMAGE = _stack_cfg.get("LPB_IMAGE_CLI", "ghcr.io/localpibox/devstack:cli")
 WEB_IMAGE = _stack_cfg.get("LPB_IMAGE_WEB", "ghcr.io/localpibox/devstack:web")
 
+# ─── Default image tag from env var ──────────────────────────────────
+# Users can set LPB_IMAGE_TAG=dev in their environment for persistent override.
+cfg_image_tag = os.environ.get("LPB_IMAGE_TAG", "")
+
 
 # ─── Version resolution (dev/main pipeline) ───────────────────────────
 # The image is built with version tags (e.g. 0.0.9-lpb-dev-cli).
@@ -166,11 +170,6 @@ def _resolve_version_image(version: str, mode: str) -> str:
     return f"ghcr.io/localpibox/devstack:{version}-{mode}"
 
 
-def _resolve_image_tag() -> str:
-    """Return the image tag suffix from env var (legacy compatibility)."""
-    return os.environ.get("LPB_IMAGE_TAG", "")
-
-
 def resolve_cli_image(tag: str) -> str:
     """Resolve the final CLI image name from stack config + tag override.
     
@@ -228,7 +227,7 @@ def _load_conf_env() -> dict[str, str]:
 
 class Config:
     image_name = CLI_IMAGE
-    image_tag = ""  # dev, main, latest, or custom tag suffix
+    image_tag = cfg_image_tag  # dev, main, latest, or custom tag suffix
     container_name = _stack_cfg.get("LPB_CONTAINER_NAME", "localpibox")
     container_cmd = ""
     port = int(os.environ.get("ED_PORT", os.environ.get("LPB_ED_PORT", _conf_cfg.get("LPB_ED_PORT", "8000"))))
@@ -879,7 +878,7 @@ def cmd_update():
     self_update()
 
     # Resolve current tag
-    tag = cfg.image_tag or _resolve_image_tag()
+    tag = cfg.image_tag
     cli_img = resolve_cli_image(tag)
     web_img = resolve_web_image(tag)
 
@@ -1022,7 +1021,7 @@ def cmd_run():
         mount_path = f"/home/lpb/workspace/{cfg.project_name}"
 
     # ── 4. Determine image and mode ──────────────────────────────────────
-    tag = cfg.image_tag or _resolve_image_tag()
+    tag = cfg.image_tag
     if cfg.web_mode:
         cfg.image_name = resolve_web_image(tag)
         mode_label = "web (VSCodium)"