Initial commit: VMware vSphere API simulator scaffold.

Add the FastAPI app, PostgreSQL migrations, Docker/Helm packaging, API
contracts, docs, client examples, and the unit/integration/compatibility
test suite for local client and tooling labs without a real vCenter.

app/contracts/store.py

@@ -0,0 +1,48 @@
+"""Immutable filesystem storage for imported contract revisions."""
+
+from __future__ import annotations
+
+import os
+import tempfile
+from dataclasses import dataclass
+from pathlib import Path
+
+from app.contracts.model import Manifest, Snapshot, canonical_json
+
+
+@dataclass(frozen=True, slots=True)
+class RevisionStore:
+    root: Path
+
+    def save(self, raw: bytes, snapshot: Snapshot, manifest: Manifest) -> Path:
+        revision = self.root / manifest.snapshot_sha256
+        if revision.exists():
+            return revision
+        self.root.mkdir(parents=True, exist_ok=True)
+        temporary = Path(tempfile.mkdtemp(prefix=".import-", dir=self.root))
+        try:
+            self._write(temporary / "raw.js", raw)
+            self._write(temporary / "snapshot.json", snapshot.canonical_bytes())
+            self._write(temporary / "manifest.json", canonical_json(manifest))
+            os.replace(temporary, revision)
+        except BaseException:
+            for child in temporary.iterdir():
+                child.unlink()
+            temporary.rmdir()
+            raise
+        return revision
+
+    def list(self) -> tuple[str, ...]:
+        if not self.root.exists():
+            return ()
+        return tuple(sorted(path.name for path in self.root.iterdir() if path.is_dir()))
+
+    def manifest(self, revision: str) -> Manifest:
+        return Manifest.model_validate_json((self.root / revision / "manifest.json").read_bytes())
+
+    @staticmethod
+    def _write(path: Path, content: bytes) -> None:
+        with path.open("xb") as stream:
+            stream.write(content)
+            stream.flush()
+            os.fsync(stream.fileno())