fixtures: golden data dir — real records, production read paths

Owner-manufactured teach master (chat_mv27rrra: compaction, subagent-abort,
every teach tool) + practice lifecycle (chat_mv293wv5: the full marker cycle
including the first-ever problem-dismissed), the real graph ledgers, five
jobs across the kind x status matrix, and settings. tests/golden-fixtures
reads all of it through the stores via the LH_DATA_DIR seam and pins the
fixture law: real data parses, flattens to a legal LLM wire, derives the
graph, covers every custom-marker kind, and reads never write.

Fixture law: an intentional format change updates these files in the same
commit; an unintentional one fails the suite.

tests/fixtures/golden-data/settings.json

@@ -0,0 +1,34 @@
+{
+	"version": 1,
+	"agent": {
+		"tools": {
+			"explain": false
+		}
+	},
+	"models": {
+		"strong": {
+			"model": {
+				"provider": "openrouter",
+				"id": "deepseek/deepseek-v4.1-flash"
+			},
+			"thinkingLevel": "low"
+		},
+		"cheap": {
+			"model": {
+				"provider": "openrouter",
+				"id": "deepseek/deepseek-v4.1-flash"
+			},
+			"thinkingLevel": "low"
+		},
+		"vision": {
+			"model": {
+				"provider": "openrouter",
+				"id": "qwen/qwen3.8-max-0902"
+			},
+			"thinkingLevel": "low"
+		}
+	},
+	"compaction": {
+		"thresholdTokens": 50000
+	}
+}