[FEATURE] Reorder Debug Overlay tabs / set a default tab

Split out from #256 (item 1) so it can be tracked and worked separately from the "copy whole request and response" feature (item 2, addressed in #268).

Request

It would be nice to be able to change the order of tabs in the Debug Overlay panel, or set a specific tab as the default one shown when the panel opens.

Context

• Tabs are defined via the DebugTab enum and rendered in DebugPanelDialog.kt (internal/ui/DebugPanelDialog.kt).
• Today the tab order is fixed by declaration order in DebugTab, and the panel always opens to the first tab.

Possible approach (to be refined)

• Allow consumers to configure tab order (and/or which tabs are enabled) via DebugOverlay's Config.
• Allow specifying a default/initial tab to show when the panel opens.