feat(structure): support search in DDL view

[0verme]

Summary

Fix #7294: after opening the table structure editor's DDL tab (e.g. via Ctrl/Cmd+click on a table name), the DDL content could not be searched with Ctrl/Cmd+F.

Root Cause

The DDL tab was rendered as a plain <pre> element and had no search UX. The global keydown handler in TableStructureEditor intercepted Ctrl/Cmd+F (it only focused the column search in the columns tab), so neither the app search UI nor the browser find would appear for the DDL tab.

(Note: DdlViewDialog.vue is a separate path and already uses a read-only CodeMirror with EditorSearchPanel — it was not part of this issue.)

Changes

• Render DDL with a lightweight read-only CodeMirror view instead of the plain <pre>.
• Reuse the existing shared EditorSearchPanel and @codemirror/search (match navigation, count display, Enter, Esc, regex / case-sensitive toggles).
• Keep the editor read-only via EditorState.readOnly.of(true).
• Handle DDL refresh, tab switching, KeepAlive deactivate/unmount cleanup, and scroll position restoration.
• Guard against duplicate shortcut handling with event.defaultPrevented.

Validation

• New targeted Vitest suites: TableStructureEditor.ddlSearch.spec.ts + TableStructureEditor.ddlSearchSource.spec.ts (5 tests passed)
• Structure-editor regression suites (primaryKey, charset/collation, concurrentTransition) passed
• vue-tsc --noEmit passed
• oxfmt --check passed
• git diff --check passed

No Rust / backend / DDL-fetch logic was changed.

[t8y2]

维护者补丁已推送（maintainerCanModify，fast-forward dca0bbda → 5cd936217）：

• 搜索面板不再遮挡「复制 DDL」按钮：给共享组件 EditorSearchPanel 增加可选的 open/close emits（对 QueryEditor/DdlViewDialog/NacosAdminConsole 等既有使用方是纯增量、零行为变化），TableStructureEditor 的 DDL tab 监听后在搜索面板打开期间隐藏同角的复制按钮。未用 CSS :has() 方案是考虑到 win7 旧 WebView 的兼容性。
• loadEditorTheme 补传 themePalette（第 4 参，与 DdlViewDialog.vue:133 的调用形态一致），修复编辑器主题=跟随应用且非默认配色时 DDL tab 与其他编辑器主题不一致的问题。
• 验证：vue-tsc 全量通过；聚焦测试 12/12 通过（ddlSearch×2、EditorSearchPanel×2、NacosAdminConsoleDelete）。

[t8y2]

Thanks for the contribution! Merged in 6d8e667, will be released in the next version.