fix(plugin-kanban): a lane that refuses the dragged card says why - #27133

Requested by Warren · project thread
Fixes #27099

维护者速读

• 改了什么:看板拖卡时,被状态机规则挡住的列除了变暗,还在 title(鼠标悬停提示)和 aria-describedby(读屏)里说明原因;泳道布局的格子同样。
• 为什么改:变暗的列不说为什么拒收,用户只会反复试或提工单;原因直接取自挡住这次移动的规则的 message,即服务端拒收同一移动时给出的那句话。
• 风险与回滚:只加属性和一个视觉隐藏的 span,开着的列与拖拽外一律不变;回滚即 revert 本 PR,无数据或元数据影响。
• 先看:ui/packages/plugin-kanban/src/ObjectKanban.tsx 的 dropBlockedReason,再看 KanbanImpl.tsx 的 dropBlockedReasonFor 与两处车道属性。
• 两分钟验证:pnpm --dir ui exec vitest run packages/plugin-kanban/src/ObjectKanban.dropBlockedReason-27099.test.tsx packages/plugin-kanban/src/__tests__/dropBlockedReason-27099.test.tsx,预期 8 个测试全绿。
• 需要你做的:无,席位落地。

Clause-②: no
Metadata-protocol: none

What changes

• KanbanImpl.tsx. KanbanBoardProps gains an optional dropBlockedReason(fromColumnId, toColumnId) beside canDropCard. While a card is dragged, a lane the gate closes now carries the reason as its title and as the text of a visually hidden span its aria-describedby names. The swimlane layout's cells, which draw the same three blocked attributes on their own, carry it the same way (one id per row and column). An open lane, and every lane outside a drag, carries neither. When the host gives no reason, the lane uses the new pack sentence kanban.dropBlocked ("A card in {{from}} cannot be moved to {{to}}.") with the two column titles.
• ObjectKanban.tsx. Supplies the reason: the message of each blocking state_machine rule on the grouped field that refuses the move. Each rule is asked alone through the gate's own read (stateMachineNextValues), so a rule the gate ignores (warning-only, inactive, insert-only, or silent on the card's value) is never named, and no second copy of the gate's predicate exists. Several closing rules join their messages; a blank message falls through to the board sentence. stateMachineNextValues and @object-ui/core are untouched.
• KanbanBoardCore.tsx. Threads the new prop, as it does canDropCard.
• @object-ui/i18n. kanban.dropBlocked in all ten packs.
• Changeset. @object-ui/plugin-kanban and @object-ui/i18n, patch.

Why

The card's Expected: a blocked lane exposes the reason the drop is refused, worded from the rule that blocks it, through a title and aria-describedby on the existing lane element, with no new widget. Measured on origin/main before the change: the only supplier of the gate is ObjectKanban's canDropCard, and the only thing it reads is the blocking state_machine rule on the groupBy field. A required field never closes a lane (it prompts after the drop), and a missing update grant makes the cards not movable, so no lane is dimmed for either. The card's "transition, required field or permission" therefore reduces to the state-machine rule, whose message the spec requires.

Tests

• ObjectKanban.dropBlockedReason-27099.test.tsx (new, beside the drop-gate test): the closed lane's title and accessible description are the rule's message; CONTROL, an open lane and every lane before the drag explain nothing; the reason leaves with the drag; two closing rules are joined while a rule silent on the from-state and a warning-only rule are not named; a blank message falls back to the board sentence.
• __tests__/dropBlockedReason-27099.test.tsx (new, real DndContext, pointer pick-up): every swimlane row's closed cell carries the reason and the open column's cells do not; the fallback is read from the zh pack under a zh provider (the two packs are first shown to differ); a host's dropBlockedReason wins over the fallback.

Acceptance notes

• The reason is the text /meta serves. The server's refusal of the same move resolves the message against objects.OBJECT._validations.RULE.message in the caller's language, but translateObject in @objectstack/spec (the served object's translation) does not touch validations[].message, and nothing in ui/ reads that key. Under a translated locale the lane therefore shows the authored text while the refusal toast would show the translated one. Reported to the seat as a finding; not changed here.
• The fallback sentence names column titles, not values, so it reads the same on every board.

Verification

All runs at head 18f0af77 (the branch with origin/main 6817bf1e merged), except the two ablations, which ran on the pre-merge commit 6dc7501f carrying the same feature diff.

Human Minimum

• 1. Schemas start as Zod; packages/spec holds no runtime logic.
• 2. Every name I added uses the casing for its kind.
• 3. No formatter ran; pnpm lint passes. (No formatter ran; pnpm lint is CI's run.)
• 4. One issue, one branch off an up-to-date main, one pull request.
• 5. A change that publishes carries a changeset, and both declaration lines are filled in here and in the changeset.
• 6. packages/spec touched: its generated artifacts are regenerated and committed. (Not touched.)
• 7. No hand edits to content/docs/references/, packages/*/CHANGELOG.md or content/docs/releases/.
• 8. Title, body and comments are in English. (The 维护者速读 block is the dispatch order's required Chinese section.)
• The Before Submitting list in CONTRIBUTING.md is done.

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