feat(stovepipe): add request log table

stovepipe/extension/storage/mysql/schema/request_log.sql

@@ -0,0 +1,16 @@
+-- request_log retains one append-only row per logical request occurrence. Exactly one of
+-- state and event is populated; core lifecycle fields remain columns, while occurrence-specific
+-- context and optional diagnostics share metadata.
+CREATE TABLE IF NOT EXISTS request_log (
+    queue                     VARCHAR(255) NOT NULL,
+    request_id                VARCHAR(255) NOT NULL,
+    log_id                    VARCHAR(255) NOT NULL,
+    timestamp_ms              BIGINT       NOT NULL,
+    state                     VARCHAR(64)  NOT NULL,
+    event                     VARCHAR(64)  NOT NULL,
+    request_version           INT          NOT NULL,
+    outcome_reason            VARCHAR(64)  NOT NULL,
+    metadata                  JSON         NOT NULL,
+    PRIMARY KEY (queue, request_id, log_id),
+    KEY idx_request_log_order (queue, request_id, timestamp_ms, log_id)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

test/integration/stovepipe/extension/storage/mysql/storage_test.go

@@ -100,6 +100,7 @@ func resetStorage(t *testing.T, db *sql.DB) {
 	t.Helper()
 
 	for _, statement := range []string{
+		"TRUNCATE TABLE request_log",
 		"TRUNCATE TABLE request_uri",
 		"TRUNCATE TABLE request",
 		"TRUNCATE TABLE build",