Task: Integrate list attachment behavior

Identity

Integrate the completed read-only task 20260831-check-list-import-attachments-c4a91f2b into main once its owner commits the task record on its isolated branch.
Verify that the source branch contains no product-code or behavior changes and preserve its documented finding that invalid roster workbook validation is correct but the immediate AgentBus reply has a gap.
Run task-aware documentation/repository checks, merge without force, push main to origin, and verify the remote ref.

The source task is read-only and proposes no canonical promotion. Do not implement its follow-up or alter product behavior in this Integration task.
Source task records are read-only from this worktree; the source owner must commit its own record before integration.
Do not deploy, restart services, mutate Kubernetes, read secrets, access ERP, retry live tasks, load the extension, or send external business messages.
If the source branch gains code changes or conflicts semantically with current canonical rules, stop and reassess before merging.

Verified source commit 97e2982 contains exactly one 44-line task record and no product code, configuration, contract, release artifact, or behavior change.
Merged the source branch into local main without conflict in merge commit b08f2960fa4db09c807b6fb61dfba33dc524a274.
Preserved the read-only finding: roster validation itself fails closed and retains awaiting_attachment; an immediate AgentBus/WeChat reply is missing only when a nominal Excel workbook reaches normalization but contains unrelated/invalid roster content.
Did not implement that follow-up because the source task proposed no behavior change and this task is limited to integration/push.
Local integration and full repository gates are complete. Remote push evidence and canonical Integrated Through finalization continue in a clean-baseline successor Integration task because the ownership checker treats a newly merged source task record as foreign relative to this task's pre-merge base.

Source worktree was clean and its ownership released before merge.
git diff --name-status 416d7e8..97e2982: exactly one added source task record.
node --run check:repo: 9/9 passed.
node --run check: passed.
node --run test:control-plane: 135/135 passed.
node --run test:legacy: 255/255 passed.
node --run build: passed.
check_project_docs.py: passed.
Merge completed without conflict; main is two commits ahead of the pre-integration remote ref before finalization.

If explicitly requested, implement and test an immediate AgentBus/WeChat result for invalid roster workbook content while preserving the original awaiting_attachment task. This merge does not authorize that product change.

None. The source task is a read-only inspection and proposes no canonical product or architecture change.