feat(01-05): commit 2 placeholder north-star assets + IOU (Path C deferral)

User invoked planning-doctrine pushback principle on the 10-20 north-star
curation step. Two 1x1 transparent-PNG placeholders ship with provenance
sidecars marked model_id: 'placeholder' so the validator exercises at >0
assets. Full deferral rationale and resolution path in
.planning/phases/01-foundations-and-doctrine/01-05-IOU.md — to be revisited
at Phase 5 entry (curate then, or amend CONTEXT D-01 if still ceremonial).

assets/north-stars/placeholder-01.png.provenance.json

@@ -0,0 +1,11 @@
+{
+  "model_id": "placeholder",
+  "checkpoint_hash": "n/a",
+  "prompt": "deferred — see .planning/phases/01-foundations-and-doctrine/01-05-IOU.md",
+  "seed": 0,
+  "sampler": "n/a",
+  "params": {
+    "note": "1x1 transparent PNG placeholder; replace with curated north-star reference at Phase 5 entry or amend CONTEXT D-01."
+  },
+  "provenance_schema_version": 1
+}