Add a structured logger and collector so runs can be traced across processes.

Sync and async sinks, redaction, and a queryable HTTP service keep concurrent logs tied to a trace id.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/example.json

@@ -0,0 +1,22 @@
+{
+  "service": "agent-squad",
+  "level": "info",
+  "modules": { "engine": "debug", "server": "warn" },
+  "sinks": [
+    { "type": "console", "format": "human", "level": "info" },
+    {
+      "type": "file",
+      "path": "logs/app.jsonl",
+      "format": "json",
+      "rotation": { "max_bytes": 104857600, "keep": 10 }
+    },
+    {
+      "type": "http",
+      "url": "http://127.0.0.1:8092/v1/logs",
+      "async": true,
+      "batch": { "max_entries": 200, "flush_interval_ms": 2000 }
+    }
+  ],
+  "redaction": { "enabled": true, "extra_patterns": [] },
+  "trace": { "generate": true, "header": "X-Trace-Id" }
+}