Implement SAND-WP-0002 meta-framework foundation (T01–T09)

Add meta-framework spec, pydantic schemas, profile/extension YAML, extension
registry, ext.compose-ssh backend, SandboxManager with State Hub events, CLI
commands, integration docs, capability registry entry, and compose-e2e runbook.
Nine unit tests pass. T10 remote smoke test remains for operator.

src/sandboxer/lifecycle/store.py

@@ -0,0 +1,52 @@
+"""Persistent sandbox status store (JSON file)."""
+
+from __future__ import annotations
+
+import json
+import os
+from datetime import UTC, datetime
+from pathlib import Path
+
+from sandboxer.models import SandboxStatus
+
+
+def _default_store_path() -> Path:
+    base = Path(os.environ.get("XDG_DATA_HOME", Path.home() / ".local" / "share"))
+    return base / "sandboxer" / "sandboxes.json"
+
+
+class SandboxStore:
+    def __init__(self, path: Path | None = None) -> None:
+        self.path = path or _default_store_path()
+        self.path.parent.mkdir(parents=True, exist_ok=True)
+
+    def _read(self) -> dict[str, dict]:
+        if not self.path.exists():
+            return {}
+        return json.loads(self.path.read_text())
+
+    def _write(self, data: dict[str, dict]) -> None:
+        self.path.write_text(json.dumps(data, indent=2, default=str))
+
+    def save(self, status: SandboxStatus) -> None:
+        data = self._read()
+        data[status.sandbox_id] = status.model_dump(mode="json")
+        self._write(data)
+
+    def get(self, sandbox_id: str) -> SandboxStatus | None:
+        raw = self._read().get(sandbox_id)
+        if not raw:
+            return None
+        return SandboxStatus.model_validate(raw)
+
+    def list_all(self) -> list[SandboxStatus]:
+        return [SandboxStatus.model_validate(v) for v in self._read().values()]
+
+    def delete(self, sandbox_id: str) -> None:
+        data = self._read()
+        data.pop(sandbox_id, None)
+        self._write(data)
+
+
+def utcnow() -> datetime:
+    return datetime.now(UTC)