修复资产计费边界风险

资产生成预扣费改为 fail-closed，避免钱包异常时继续调用外部生成

新增钱包退款 outbox，退款失败时本地落盘并后台重放

拼图首图后台任务改用 SpacetimeDB claim 表实现跨实例互斥

计费 ledger id 统一绑定 request_id，并让前端重试复用 x-request-id

同步 SpacetimeDB bindings、后端架构文档和 Hermes 决策记录

server-rs/crates/spacetime-client/src/mapper/puzzle.rs

@@ -13,6 +13,16 @@ pub(crate) fn map_puzzle_agent_session_procedure_result(
     Ok(map_puzzle_agent_session_snapshot(session))
 }
 
+pub(crate) fn map_puzzle_background_compile_task_procedure_result(
+    result: PuzzleBackgroundCompileTaskProcedureResult,
+) -> Result<bool, SpacetimeClientError> {
+    if !result.ok {
+        return Err(SpacetimeClientError::procedure_failed(result.error_message));
+    }
+
+    Ok(result.claimed)
+}
+
 pub(crate) fn map_puzzle_work_procedure_result(
     result: PuzzleWorkProcedureResult,
 ) -> Result<PuzzleWorkProfileRecord, SpacetimeClientError> {
@@ -614,6 +624,23 @@ pub struct PuzzleFormDraftSaveRecordInput {
     pub saved_at_micros: i64,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PuzzleBackgroundCompileTaskClaimRecordInput {
+    pub task_id: String,
+    pub claim_id: String,
+    pub session_id: String,
+    pub owner_user_id: String,
+    pub claimed_at_micros: i64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PuzzleBackgroundCompileTaskReleaseRecordInput {
+    pub task_id: String,
+    pub claim_id: String,
+    pub session_id: String,
+    pub owner_user_id: String,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct PuzzleAgentMessageSubmitRecordInput {
     pub session_id: String,