Task: Fix AgentBus attachment rejection reply

Identity

Diagnose why a structured AgentBus roster attachment that returns input_attachment.status = rejected leaves the original task waiting but sends no rejection feedback to the channel user.
Add an attempt-level failed result for rejected roster attachments in both legacy in-memory and database-backed durable AgentBus delivery modes.
Preserve the original task's awaiting_attachment state, avoid scheduling parsing for rejected bytes, and add focused regression coverage.
Run the full repository gates, commit the bounded fix on main, and push it non-forced to origin/main.

Keep the existing fail-closed roster workflow: a rejected workbook must not enter Program parsing or ERP execution, and the same waiting task must remain available for a corrected attachment.
Return the existing bounded input_attachment.message; do not expose attachment URL, hostname, IP, file name, workbook bytes, cell values, raw converter output, or unsafe error details.
Preserve the durable accepted/result outbox, inbound frame reply routing, conversation correlation, and idempotent delivery keys.
Do not deploy, restart services, mutate Kubernetes, access ERP, read secrets, retry the live task, or send an external message.

Confirmed the feedback gap was not an AgentBus transport exception. Workbook rejection is represented as a successful TaskMessageResult while the business task intentionally remains awaiting_attachment; therefore the generic exception reply did not run and the terminal-task finalizer correctly skipped the still-waiting task.
Added an explicit attachment-attempt rejection branch immediately after task ingestion. It emits a failed task.result through the database outbox for durable channels or the existing pending-reply path for legacy listeners, then returns without requesting the parse queue.
Kept the task state and reusable waiting workflow unchanged. The channel receives the existing safe workbook rejection text and can submit a corrected .xls/.xlsx attachment in a later message.
Added direct-listener and durable-channel regressions covering reply routing, failure status/text, retained waiting state, and zero parse-queue requests.

Focused AgentBus tests: 16/16 passed.
node --run check:repo: 10/10 passed.
node --run check: passed.
node --run test:control-plane: 139/139 passed.
node --run test:legacy: 256/256 passed.
node --run build: passed.
check_project_docs.py: passed.
check_doc_drift.py --task-id 20260831-fix-agentbus-attachment-reply-6f2c9a41: passed.
git diff --check: passed.

Deploy/restart and verify the corrected reply with a real WeChat attachment only under separate authorization.

Target canonical AgentBus/data-flow memory during a later Integration task.
Proposal: roster workbook rejection is an attachment-attempt failure that must create an immediate failed AgentBus result even though the reusable business task remains nonterminal in awaiting_attachment.
Evidence: control-plane/src/agentbus.ts, control-plane/test/agentbus.test.ts, and the focused 16/16 AgentBus regression.
Human confirmation required: no for the bounded reply behavior; deployment and live retry remain separately authorized.