Web details default closed
Web 详情栏默认关闭
The transient layout store initialized details to its 360px contract width. The first connected Session and every full reload therefore reserved a right column before the user selected any detail content. Chat tool rows deliberately remain inline and do not open details, while Trajectory rows open the panel when an event is selected, so an open layout default did not represent an active detail selection.
English
Problem
The transient layout store initialized details to its 360px contract width. The first connected Session and every full reload therefore reserved a right column before the user selected any detail content. Chat tool rows deliberately remain inline and do not open details, while Trajectory rows open the panel when an event is selected, so an open layout default did not represent an active detail selection.
Decision
The layout store initializes details to zero while retaining the existing 360px contract default for openDetails(). AppFrame keeps the details slot mounted at zero width, so an explicit entry point such as Trajectory event selection can open the panel without remounting its subtree. The Session ownership lifecycle remains authoritative: unselected surfaces derive zero width without taking ownership, returning to the same Session preserves an explicitly opened width, and selecting a different Session closes it.
Panel geometry remains transient. No browser storage key is introduced, and reload restores the sidebar default while details returns to zero. Component tests pin the store default, mounted zero-width slot, drag and concession behavior after explicit opening, and Session ownership transitions. The keyless shipped-composition regression pins the closed first Session, reload, new-session surface, and subsequent Session selections.
Alternatives considered
Persist the last open or closed preference. Rejected because reload should have a deterministic closed baseline, and persisting geometry would reintroduce stale viewing state across browser sessions.
Keep details open until Chat receives a replacement selection gesture. Rejected because empty space is not useful detail content. Chat's inline tool-row interaction and any future detail-selection gesture are separate product decisions.
Remove the details column and layout service. Rejected because Trajectory already opens event details through this seam, and keeping the mounted slot preserves that working interaction.
Consequences
New, restored, and reloaded Sessions use the full center area until an explicit details action opens the right column. Trajectory event selection can still open details at 360px and its close control returns the track to zero; Chat tool rows remain geometry-inert. Switching to another Session closes an opened panel, and no panel state survives reload.
中文
问题
瞬时布局 store 原本将详情栏初始化为 360px 的契约宽度。因此，首个已连接会话以及每次完整重新加载都会在用户选择任何详情内容之前预留右侧栏。Chat 工具行有意保持内联，不会打开详情栏；Trajectory 行则会在选中事件时打开详情栏。因此，布局默认打开并不表示存在有效的详情选中项。
决策
布局 store 将详情栏初始化为零，同时保留 openDetails() 现有的 360px 契约默认宽度。AppFrame 仍以零宽度挂载详情 slot，因此 Trajectory 事件选择等显式入口可以打开详情栏，而无需重新挂载其子树。会话所有权生命周期仍是权威契约：未选中表面会派生零宽度而不取得所有权；返回同一会话时会保留显式打开后的宽度；选择不同会话时则会关闭详情栏。
面板几何信息仍是瞬时状态。系统不新增浏览器存储键；重新加载会恢复侧边栏默认值，并使详情栏回到零宽度。组件测试固定验证 store 默认值、保持挂载的零宽度 slot、显式打开后的拖动与让步行为，以及会话所有权过渡。无密钥的已交付组合回归测试固定验证首个会话保持关闭、重新加载、New Session 表面和后续会话选择。
考虑过的替代方案
持久化最后一次打开或关闭的首选状态。 之所以否决：重新加载必须具有确定的关闭基线，而持久化几何信息会在浏览器会话之间重新引入陈旧的查看状态。
在 Chat 获得替代性的选择手势前保持详情栏打开。 之所以否决：空白区域不是有用的详情内容。Chat 的内联工具行交互与未来可能增加的详情选择手势属于彼此独立的产品决策。
移除详情栏和布局服务。 之所以否决：Trajectory 已经通过该服务边界打开事件详情；继续挂载该 slot 可以保留这一正常工作的交互。
后果
新建、恢复和重新加载的会话会使用完整的中央区域，直至显式详情操作打开右侧栏。Trajectory 事件选择仍可将详情栏打开至 360px，其关闭控件会使轨道回到零；Chat 工具行仍不改变几何信息。切换到其他会话会关闭已打开的详情栏，并且任何面板状态都不会在重新加载后保留。