feat: profiles registry read/write + find

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

gates/profiles.py

@@ -0,0 +1,48 @@
+"""Named-profile registry + dir ops for the Image Pool. Stdlib only."""
+import json
+import os
+import shutil
+import zipfile
+from pathlib import Path
+
+REGISTRY_NAME = "profiles.json"
+
+
+def registry_path(base):
+    return Path(base) / REGISTRY_NAME
+
+
+def empty_registry():
+    return {"profiles": []}
+
+
+def read_registry(base):
+    p = registry_path(base)
+    if not p.exists():
+        return empty_registry()
+    try:
+        with open(p, "r", encoding="utf-8") as f:
+            reg = json.load(f)
+        if not isinstance(reg, dict) or "profiles" not in reg:
+            raise ValueError("bad registry")
+        return reg
+    except (ValueError, json.JSONDecodeError):
+        return empty_registry()
+
+
+def write_registry(base, reg):
+    Path(base).mkdir(parents=True, exist_ok=True)
+    final = registry_path(base)
+    tmp = final.with_name(REGISTRY_NAME + ".tmp")
+    with open(tmp, "w", encoding="utf-8") as f:
+        json.dump(reg, f, indent=2)
+    os.replace(tmp, final)
+    return reg
+
+
+def find_by_id(reg, pid):
+    return next((p for p in reg["profiles"] if p["id"] == pid), None)
+
+
+def find_by_name(reg, name):
+    return next((p for p in reg["profiles"] if p["name"] == name), None)