Add support for interactive panel docking

[Keavon]

Partly closes#195

capture_4_.mp4

[cubic-dev-ai]

4 issues found across 8 files

Confidence score: 2/5

• High-risk merge: there are concrete, high-confidence data-loss paths in editor/src/messages/portfolio/portfolio_message_handler.rs where SplitPanelGroup and MoveAllPanelTabs remove/clear tabs before validating target_group, so invalid targets can drop tabs.
• editor/src/messages/portfolio/utility_types.rs can return a fresh PanelGroupId even when split insertion fails, creating state drift where subsequent lookups/mutations target an ID not present in the layout tree.
• frontend/wrapper/src/editor_wrapper.rs uses unwrap() while decoding JS input; malformed input can panic and crash the editor runtime, making this a user-visible stability risk.
• Pay close attention to editor/src/messages/portfolio/portfolio_message_handler.rs, editor/src/messages/portfolio/utility_types.rs, and frontend/wrapper/src/editor_wrapper.rs - tab-loss ordering, invalid ID/state drift, and panic-on-decode need guarding before merge.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.
<file name="frontend/wrapper/src/editor_wrapper.rs">
<violation number="1" location="frontend/wrapper/src/editor_wrapper.rs:478">
P2: Avoid `unwrap()` when decoding JS inputs in this wrapper method; malformed input can panic and crash the editor runtime.</violation>
</file>
<file name="editor/src/messages/portfolio/utility_types.rs">
<violation number="1" location="editor/src/messages/portfolio/utility_types.rs:241">
P2: `split_panel_group` returns a newly generated `PanelGroupId` even when the insertion fails. That ID is not present in the layout tree, so any follow-up lookup/mutation will fail or drift from the real state. Consider returning `Option<PanelGroupId>` (or the existing group ID) and only returning `Some(new_id)` when insertion succeeds.</violation>
</file>
<file name="editor/src/messages/portfolio/portfolio_message_handler.rs">
<violation number="1" location="editor/src/messages/portfolio/portfolio_message_handler.rs:472">
P1: `MoveAllPanelTabs` does not validate `target_group` before clearing the source tabs, so an invalid target can drop all moved tabs.</violation>
<violation number="2" location="editor/src/messages/portfolio/portfolio_message_handler.rs:1288">
P1: `SplitPanelGroup` can lose dragged tabs when `target_group` is invalid because tabs are removed before split insertion is validated.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[gemini-code-assist]

Code Review

This pull request implements advanced panel docking and tab management features, including the ability to move entire tab groups and split panel groups via drag-and-drop. The implementation introduces new message types, updates the workspace layout logic, and adds visual feedback in the frontend. Feedback was provided regarding the efficiency of inserting elements into a vector, the use of a sentinel value for list insertion, and the performance impact of frequent DOM queries during drag operations.