A tile whose owned query is missing or shared cannot be removed from any surface

src/dashboard/application/dashboard-removal.ts:128-131 から始め、Dashboards ツリーのごみ箱とタイルヘッダーの Remove tile の各経路を、既存の remove-tile コマンドも含めて追跡します。クエリが存在しない場合にどのドキュメント化されたオプションを適用するかを判断し、共有クエリに対する拒否は維持します。関連するサーフェスから、クエリを削除せずに孤立したタイルに対して選択した削除経路が機能すれば完了です。

Problem

removeDashboardPanel proves ownership before deleting anything and refuses
ownership-unproven when the tile's queryId names no query in
workspace.queries, or names one with more than one owner
(src/dashboard/application/dashboard-removal.ts:128-131). Both the Dashboards
tree and — since #537 — the tile header route their delete through it.

That is the correct fail-closed behaviour #494/#537 specify. The consequence is
that a tile whose query is missing (a dangling queryId) or shared by a
second tile now has no removal path from any surface:

• the Dashboards-tree trash is disabled with a reason;
• the tile header's ⋯ → Remove tile row is disabled with the same reason;
• and #537 deleted the last escape hatch — the tile head's old document-only
  remove-tile dispatch, which removed such a tile without touching queries.

How to reach it

A queries-only bundle import (#448) or a corrupt aggregate can produce a tile
pointing at an id no query carries. A legacy or hand-edited workspace can carry
two tiles referencing one query, which #427 forbids reaching but does not
retroactively repair.

Why it was deferred

#537's acceptance criteria require exactly this fail-closed behaviour, so the
alternative belongs in its own decision rather than smuggled into that change.

Options

1. A separate, explicitly-labelled "Remove tile only" action, offered only
   when removal is refused because the query is missing — a dangling reference has
   no second resource to be atomic about. Would keep the remove-tile command,
   which currently has no UI dispatcher left.
2. Give removeDashboardPanel an explicit tile-only arm for the missing-query
   case, so one path still covers it.
3. Accept it, and handle these workspaces through Import/Replace only.

Option 1 or 2 seems right for the missing-query case; a shared query arguably
should stay unremovable, since either tile still renders it.