[turinglambdaai]

P0 — user-reported data correctness issue

Reproduction: select 生活, enter a plain task and press Enter; Taskly writes it to 工作. The Windows host passed std::nullopt as the list_id argument of add_task_async, so the backend silently chose the database's first list (工作), unlike the macOS and Linux hosts.

Changes

• Never infer a task destination inside the backend for Windows quick add. Resolve a concrete target ID at submit time: named list → its ID; smart view → first list; no valid target → keep the draft and show taskCreateListFirst. Capture that ID by value across both async parse and save callbacks, so changing the view while the operation runs cannot redirect a task.
• Reject stale snapshot response rendering after a view/list switch, then retry loading the newly selected view; avoids showing a previous list's rows under the newly selected heading.
• Rebuild WinUI task row as a two-row grid: checkbox and title share centered row 0; only actual due/notes content is placed below, in row 1. A plain task with no date/time/notes has no empty metadata row or misaligned title.
• Add stable, user-facing UIA IDs for list rows, task rows, list creation dialog input and current view title. Add Windows packaged E2E regression: create 生活 next to default 工作, choose 生活, add via the actual Enter key, confirm task is present there and absent from 工作, switch away/back to verify persistence, and check checkbox/title vertical center on the metadata-free row.
• Add matching explicit cross-platform product-contract rules in PRODUCT-SPEC.md.

Dependency

This branch includes #32's verified quick-add draft-preservation changes, because it is based on fix/windows-quick-add-preserve-draft. Merge #32 before this PR, then inspect the reduced diff. It does not include #26 startup or #31 input underline.

Acceptance before merging

• Windows native CI and packaged product acceptance both green on this commit.
• Manual Windows 10/11: create 生活, select it, add multiple plain tasks by Enter; confirm no task appears in 工作. Repeat after changing view during async request and after restart.
• Check checkbox/title alignment and density at 100% / 150% DPI and light/dark themes, including tasks with due dates and notes.
• Check quick add in 全部 and 计划: the first-list fallback remains consistent with macOS/Linux; no-list and failing save preserve drafts.
• macOS/Linux regression checks; follow-up multi-select / bulk UI parity tracked separately.

Do not merge or release until these gates are met.