Fix text selection not starting over markdown tables

[zachlloyd]

Description

Fixes being unable to start a text selection inside a rendered Markdown table in agent output (e.g. clicking and dragging within a table no longer does nothing).

Root cause: The WarpUI Table paints its row/header backgrounds and dividers with draw_rect_with_hit_recording, in a paint layer above the enclosing SelectableArea. On LeftMouseDown, SelectableArea bails when the point is "covered" (event.at_z_index(...).is_none()), so a mouse-down that originates over the table never starts a selection. Drag events aren't subject to that coverage check, which is exactly why starting a selection outside the table and dragging in worked, but starting inside the table did nothing.

Fix: Mark the Table's body paint layer click-through (set_active_layer_click_through) so its decorative chrome no longer makes the underlying SelectableArea treat the point as covered. This mirrors the notebook/editor table renderer (crates/editor/src/render/element/table.rs), which already marks its paint layer click-through.

https://www.loom.com/share/7dd109b714324afb82d08c88adb758e1

Linked Issue

#12751

• The linked issue is labeled ready-to-spec or ready-to-implement.
• Where appropriate, screenshots or a short video of the implementation are included below.

Testing

• cargo fmt and cargo clippy -p warpui_core -- -D warnings pass.

• Verified the behavior with computer use using the table-sample example's selection demo (screenshot below): a click-drag that starts inside the table now selects text.

• Follow-up: a deterministic regression test can be added in crates/warpui_core/src/elements/table/mod_tests.rs (App::test harness) asserting that a LeftMouseDown over a Table inside a SelectableArea starts a selection.

• I have manually tested my changes locally

Screenshots / Videos

Computer-use verification screenshot attached in the originating Oz conversation.

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

Conversation: https://staging.warp.dev/conversation/9b55249d-1f57-4c94-87d0-c696c19628bf
Run: https://oz.staging.warp.dev/runs/019ed67b-be88-7b9d-94f4-24714fca3f2e

This PR was generated with Oz.

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@zachlloyd

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Overview

This PR marks the WarpUI table body paint layer as click-through so table chrome no longer prevents the enclosing SelectableArea from receiving mouse-down events that start text selection inside rendered markdown tables.

Concerns

• ⚠️ [IMPORTANT] For this user-facing behavior change, the attached review context does not include a direct screenshot or screen recording. The description only says the screenshot is attached in the originating Oz conversation, so please attach visual evidence to the PR demonstrating selection starting inside a rendered markdown table.
• 💡 [SUGGESTION] Consider adding the deterministic SelectableArea/Table regression test described in the PR so this hit-testing path remains covered.

Verdict

Found: 0 critical, 1 important, 1 suggestion

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