Record U2/U4 receipts and the U10 fail-stop in the task card

Why: keep the per-unit audit trail; U10 first run failed-unknown
(pi attempt exited 0 without a decodable terminal record), workspace
preserved for reconciliation and the unit re-dispatched with a corrected
packet (nested deps gitlinks materialized).
Evidence: verify-u2/u4/u4b exit=0; no code change.
Impact: task metadata only.
Refs: feature/agent-stack-audit-remediation-b1

.task/feature-agent-stack-audit-remediation-b1.md

@@ -35,7 +35,11 @@
 | agent-stack-b1-u1-native-workspace | native: adapters/native/backend.go+test, runtime/tools/{exec,jail,atomic}.go+test | digest 见 /tmp/agent-stack-b1/u1-run.json | implementation | [cursor, antigravity, pi-glm, pi, codex] | 1 | cursor-agent-stable | success | refs/agent-exec/e10eca84…/18a9b3caba61 → native 81e5bf3（transport 273213a 重写为规范提交） | 否 | /tmp/agent-stack-b1/u1-run.json |
 | agent-stack-b1-u5-intent-snapshot-generated | intent: intent/（fold/registry/catalog/recognizer/slots/generator+tests） | digest 见 /tmp/agent-stack-b1/u5-run.json | implementation | 同上 | 1 | cursor-agent-stable | success | refs/agent-exec/357b5d70…/90a2c1b0488f → intent 765a7e7 | 否 | /tmp/agent-stack-b1/u5-run.json |
 | agent-stack-b1-u7a-command-isolation | command: registry.go/result.go/conformance/+tests | digest 见 /tmp/agent-stack-b1/u7a-run.json | implementation | 同上 | 1 | cursor-agent-stable | success | refs/agent-exec/243aef44…/2e0a169b7174 → command fe7987d | 否 | /tmp/agent-stack-b1/u7a-run.json |
-| u2/u4/u10 | wave B 派发中（native/squad/backend） | — | implementation | 同上 | — | — | running | — | — | /tmp/agent-stack-b1/{u2,u4,u10}-run.json |
+| u2-native-session-contract | native: contract.go/backend.go/session/tree.go/tools+regression tests | digest 见 /tmp/agent-stack-b1/u2-run.json | implementation | 同上 | 1 | cursor-agent-stable | success | transport f7a3ff39 重写为规范提交（基于 81e5bf3） | 否 | /tmp/agent-stack-b1/u2-run.json |
+| u4-squad-resolver-config | squad: squad/backend.go+config_identity.go, adapters/native/register.go+tests | digest 见 /tmp/agent-stack-b1/u4-run.json | implementation | 同上 | 1 | cursor-agent-stable | success | squad 3a98d873 → aa15a5d 规范提交 | 否 | /tmp/agent-stack-b1/u4-run.json |
+| u10-backend-scoped-config（首次） | backend: internal/app|runtime|squadadapter | digest 见 /tmp/agent-stack-b1/u10-run.json | implementation | [pi, codex]（cursor/agy 临时禁用） | 1 | pi MiniMax-M3 | failed-unknown（fail-stop：退出码 0 但无有效终态记录） | 无 transport，不采用 | 否 | /tmp/agent-stack-b1/u10-run.json；现场保留 /tmp/agent-exec-1000/b627ce2c41c90bea0d9f78270819d419 待对账 |
+| u10-backend-scoped-config（重派） | 同上；包修正：allowed_paths 补嵌套 deps gitlink，禁止 -modfile 变通 | digest 见 /tmp/agent-stack-b1/u10b-run.json | implementation | [pi, codex] | — | — | running | — | — | /tmp/agent-stack-b1/u10b-run.json |
+| u3a-native-result-fidelity | native: exec/、adapters/native/、runtime/loop.go | digest 见 /tmp/agent-stack-b1/u3a-run.json | implementation | 同上 | — | — | running | — | — | /tmp/agent-stack-b1/u3a-run.json |
 
 ## 关联方向与规划
 
@@ -64,7 +68,7 @@
 | 需求表确认 | 本卡 R1-R7 | 已完成 | host | 2026-10-21 | 方案 Requirements |
 | 方案设计 | 方案文档 d3161347 | 已完成 | 前序会话 | 2026-10-21 | F01-F16 |
 | 实施计划 | 本卡波次表 | 已完成 | host | 2026-10-21 | U1-U7/U10 依赖 |
-| 实施与自检 | wave A: native 81e5bf3 / intent 765a7e7 / command fe7987d | wave A 完成，验证 PASS | agent-per-unit(cursor attempt1) + host 验证 | 2026-10-21 | verify-{u1,u5,u7a}.json 均 exit=0 |
+| 实施与自检 | wave A+U2+U4 完成；U10 首轮 fail-stop 保留现场后重派；U3a 派发中 | 进行中 | agent-per-unit + host 验证 | 2026-10-21 | verify-{u1,u5,u7a,u2,u4,u4b}.json 均 exit=0 |
 | 正式测试与验收 | 待定 | 待执行 | — | — | — |
 | 代码 Review | 待定 | 待执行 | — | — | — |
 | 合入 | 待定 | 待执行 | — | — | — |