fix: never report "nothing pending" when the package index is gone, and load it on request

OpenWrt keeps its package index in RAM. After a reboot `apk version` only
warns that it cannot open its cached index and exits 0, and `opkg
list-upgradable` prints nothing: both read as "no updates". netOrk keeps
"pending since" per package (MVP 5), so the reader now raises instead:

- apk: on apk's own warning ("opening from cache ... No such file"), or a
  failed exit status.
- opkg: when /var/opkg-lists is empty.
- refresh_available_updates(): apk update / opkg update, success from the
  exit status.

napalm_openwrt/system_mixin.py

@@ -18,6 +18,20 @@ import time as _time
 from typing import Any
 
 
+
+#: Printed after a command so its exit status survives the shell session.
+_RC_MARKER = "__OWRT_RC="
+_RC_RE = re.compile(rf"^{_RC_MARKER}(\d+)\s*$", re.MULTILINE)
+#: What apk prints when its index is not in RAM (after a reboot).
+_APK_INDEX_MISSING = re.compile(r"opening from cache .*No such file or directory")
+
+
+def _split_status(raw: str) -> tuple[str, int | None]:
+    """``(output, exit_status)``; the status is None when the marker never arrived."""
+    statuses = _RC_RE.findall(raw or "")
+    output = _RC_RE.sub("", raw or "").strip()
+    return output, int(statuses[-1]) if statuses else None
+
 class OpenWrtSystemMixin:
     """Mixin providing system-level NAPALM getters (environment, NTP, SNMP, users, services, updates, device actions)."""
 
@@ -593,37 +607,64 @@ class OpenWrtSystemMixin:
         return warnings
 
     def get_available_updates(self) -> list[dict[str, Any]]:
-        """Return list of upgradable packages from the local package manager cache."""
-        import re as _re
-        pm = self._pm_type()
-        updates: list[dict[str, Any]] = []
+        """Return list of upgradable packages from the local package manager cache.
 
-        if pm == "apk":
-            # Output format: "pkgname-current_ver < new_ver"
-            raw = self._send_command("apk version 2>/dev/null | grep '<'")
-            for line in raw.splitlines():
-                line = line.strip()
-                m = _re.match(r'^(.+)-(\d\S*)\s+<\s+(\S+)', line)
-                if m:
-                    updates.append({
-                        "name": m.group(1),
-                        "current_version": m.group(2),
-                        "new_version": m.group(3),
-                    })
+        OpenWrt keeps its package index in RAM. Without it -- after a reboot,
+        before ``refresh_available_updates`` -- ``apk version`` only warns and
+        ``opkg list-upgradable`` prints nothing. Both raise here instead of
+        reporting "nothing pending".
+        """
+        if self._pm_type() == "apk":
+            updates = self._updates_apk()
         else:
-            # opkg output: "pkgname - current_ver - new_ver"
-            raw = self._send_command("opkg list-upgradable 2>/dev/null")
-            for line in raw.splitlines():
-                parts = [p.strip() for p in line.split(" - ")]
-                if len(parts) == 3:
-                    updates.append({
-                        "name": parts[0],
-                        "current_version": parts[1],
-                        "new_version": parts[2],
-                    })
-
+            updates = self._updates_opkg()
         return sorted(updates, key=lambda u: u["name"])
 
+    def _updates_apk(self) -> list[dict[str, Any]]:
+        import re as _re
+
+        output, status = _split_status(self._send_command(f"apk version 2>&1; echo {_RC_MARKER}$?"))
+        if status != 0:
+            raise RuntimeError(f"apk version failed (exit {status}): {output[-200:]}")
+        if _APK_INDEX_MISSING.search(output):
+            raise RuntimeError("The package index is not loaded (run apk update first)")
+        updates: list[dict[str, Any]] = []
+        for line in output.splitlines():
+            # Output format: "pkgname-current_ver < new_ver"
+            m = _re.match(r"^(.+)-(\d\S*)\s+<\s+(\S+)", line.strip())
+            if m:
+                updates.append({
+                    "name": m.group(1),
+                    "current_version": m.group(2),
+                    "new_version": m.group(3),
+                })
+        return updates
+
+    def _updates_opkg(self) -> list[dict[str, Any]]:
+        raw = self._send_command(
+            '[ -n "$(ls /var/opkg-lists 2>/dev/null)" ] || echo __NO_INDEX__; '
+            "opkg list-upgradable 2>/dev/null"
+        )
+        if "__NO_INDEX__" in raw:
+            raise RuntimeError("The package index is not loaded (run opkg update first)")
+        updates: list[dict[str, Any]] = []
+        for line in raw.splitlines():
+            # opkg output: "pkgname - current_ver - new_ver"
+            parts = [p.strip() for p in line.split(" - ")]
+            if len(parts) == 3:
+                updates.append({
+                    "name": parts[0],
+                    "current_version": parts[1],
+                    "new_version": parts[2],
+                })
+        return updates
+
+    def refresh_available_updates(self) -> dict[str, Any]:
+        """Load the package index into RAM (``apk update`` / ``opkg update``)."""
+        cmd = "apk update" if self._pm_type() == "apk" else "opkg update"
+        output, status = _split_status(self._send_command(f"{cmd} 2>&1; echo {_RC_MARKER}$?"))
+        return {"success": status == 0, "output": output}
+
     def apply_updates(self, packages: list[str]) -> dict[str, Any]:
         """Upgrade the given packages using the device's package manager."""
         import re as _re