Implement phase-memory foundation

tests/fixtures/memory-graph.json

@@ -0,0 +1,56 @@
+{
+  "schema_version": "markitect.memory.graph.v1",
+  "id": "phase-memory-fixture-graph",
+  "nodes": [
+    {
+      "id": "decision.boundary",
+      "kind": "decision",
+      "text": "Markitect owns syntax contracts; phase-memory owns runtime phase planning.",
+      "phase": "stabilized",
+      "source_spans": [{"path": "docs/architecture.md", "line_start": 1}],
+      "metadata": {"title": "Boundary decision"}
+    },
+    {
+      "id": "event.restart",
+      "kind": "episode",
+      "text": "Restart package should include boundary decision and active graph neighborhood.",
+      "phase": "fluid",
+      "freshness": {"updated_at": "2026-05-01T00:00:00+00:00", "source_digest": "old"}
+    },
+    {
+      "id": "artifact.profile",
+      "kind": "artifact",
+      "text": "Memory profile declares budgets, stores, retention, activation, policy, and fallback behavior.",
+      "phase": "stabilized",
+      "freshness": {"updated_at": "2026-05-18T00:00:00+00:00", "source_digest": "fresh"}
+    },
+    {
+      "id": "risk.durable-write",
+      "kind": "risk",
+      "text": "Durable writes must stay review gated until the runtime plan is explicit.",
+      "phase": "fluid"
+    }
+  ],
+  "edges": [
+    {
+      "id": "edge.boundary-profile",
+      "kind": "governs",
+      "source": "decision.boundary",
+      "target": "artifact.profile"
+    },
+    {
+      "id": "edge.risk-boundary",
+      "kind": "depends_on",
+      "source": "risk.durable-write",
+      "target": "decision.boundary"
+    }
+  ],
+  "events": [
+    {
+      "id": "event.activation",
+      "kind": "activated",
+      "timestamp": "2026-05-18T00:00:00+00:00",
+      "activation_refs": ["activation.fixture"]
+    }
+  ]
+}

tests/fixtures/memory-profile.json

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+{
+  "schema_version": "markitect.memory.profile.v1",
+  "id": "phase-memory-fixture-profile",
+  "title": "Phase Memory Fixture Profile",
+  "intent": "Plan reasoning, conversation, knowledge, and activation memory behavior.",
+  "memory_kinds": ["reasoning", "conversation", "knowledge", "package"],
+  "stores": {
+    "reasoning": "local-graph-store",
+    "conversation": "local-event-log",
+    "knowledge": "local-graph-store",
+    "package": "markitect-context-package"
+  },
+  "limits": {
+    "reasoning": {"max_nodes": 40},
+    "conversation": {"max_nodes": 20},
+    "package": {"max_items": 3}
+  },
+  "retention": {
+    "conversation": {"stale_after_days": 7, "delete_after_days": 30}
+  },
+  "refresh": {
+    "trigger": "source-artifact-or-profile-digest-change"
+  },
+  "compaction": {
+    "strategy": "summarize-trace-after-review"
+  },
+  "activation": {
+    "max_items": 3,
+    "max_tokens": 30
+  },
+  "policy": {
+    "required_labels": ["project-local"],
+    "durable_writes": "review-gated",
+    "secrets_allowed": false
+  },
+  "observability": {
+    "emit_events": true
+  },
+  "failure": {
+    "missing_runtime_store": "degrade-to-dry-run"
+  },
+  "metadata": {
+    "derived_from": ["MKTT-WP-0016", "IB-WP-0017"]
+  }
+}