Agent chat input mouse cursor changes from I-beam to arrow after clicking

Describe the bug

Clicking the agent/chat text input changes the mouse pointer from an I-beam to the standard arrow while it remains over editable text. Terminal-mode input was not affected in local reproduction; switching windows was not required.

To reproduce

1. Open an agent conversation with transcript content.
2. Hover over the chat input and observe the I-beam.
3. Click to focus the input and begin typing.
4. Observe the pointer changing to an arrow.

Expected behavior

The pointer remains an I-beam over the editable input after clicking.

Environment

• Ubuntu Linux, zsh 5.9.
• Desktop session: Wayland; debug GUI reproduced via X11/Vulkan.
• Investigated source commit: 1e6c3ae. Installed release version and regression history not recorded.

Investigation

Cursor-only instrumentation captured an IBeam set for the input followed by AIBlockAction::SelectText calling ctx.reset_cursor() at app/src/ai/blocklist/block.rs:6623, via ViewContext::reset_cursor.

SelectText unconditionally resets the cursor even for empty/cleared selections. The input Hoverable only sets the I-beam on hover transitions, so the arrow persists while the pointer stays inside.

The proposed fix moves reset_cursor into the existing has_selection guard. The extended copy_selected_text_from_ai_block regression fails before the fix (actual Arrow, expected IBeam for an empty selection) and passes afterward. It also verifies real selections still reset to Arrow and clearing a selection preserves the input cursor.

Manual verification: the reporter ran the patched local GUI build and confirmed that the cursor issue is fixed. The chat input retains the I-beam after clicking. Existing GitHub searches found no direct duplicate.