feat(devtools): read-only display mode and panel-bounded fullscreen (SKY-536)

[harijoe]

Stacked on #1044 (SKY-535). Review only the last commit.

What

The display mode stops being user-controlled in the tool panel: it is driven only by the view.

• The inline/pip/fullscreen buttons are replaced by a static badge showing the current mode (muted fill, no border, tooltip). The mode changes only when the widget requests it via requestDisplayMode / ui/request-display-mode.
• displayMode is removed from the devtools_set_view_options WebMCP form, so agents can't set it either. The chatgpt-app-builder skill reference is updated to match.
• Fullscreen is bounded to the tool panel work area instead of the whole devtools body: the ToolPanel root becomes the positioned ancestor of the fullscreen overlay, so the tools sidebar and header stay visible. The exit paths (cross button, ESC) are unchanged.
• displayMode is no longer persisted (store version 2, migration drops it from v1 blobs). A stale persisted fullscreen would otherwise reopen the panel in fullscreen with no control left to explain or undo it; now every session starts inline and the view drives it from there.

[greptile-apps]

Greptile Summary

The PR makes display mode view-controlled, removes it from persisted and WebMCP-configurable preferences, and bounds fullscreen rendering to the tool-panel workspace.

• Replaces display-mode controls with a read-only status badge.
• Migrates persisted preferences to omit display mode.
• Makes the tool-panel root the fullscreen overlay’s positioned ancestor.
• Updates the app-builder reference to match the revised WebMCP interface.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

_{Reviews (5): Last reviewed commit: "feat(devtools): read-only display mode i..." | Re-trigger Greptile}

[harijoe]

@greptileai