Fix stale iTerm2 inline images on redraw

Description

Redrawing a transparent iTerm2 inline image at the same cursor position leaves the previous image visible underneath it. This causes stale graph lines to accumulate when scrolling in Serie with --protocol iterm.

Remove existing iTerm image placements at the same anchor before placing the replacement image, after validating the incoming image. Images anchored elsewhere and Kitty image placements are preserved.

Linked Issue

Fixes #16586

• 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 (especially for user-visible or UI changes).

The linked issue has a standalone reproduction and is labeled bug and repro:high. This is a reproducible bug fix submitted directly as a code PR under the contribution guide.

Testing

Tested on macOS 15.7.3 (Apple Silicon) with Rust 1.92.0.

• cargo nextest run --locked -p warp_terminal: 560 passed, 2 existing ignored tests skipped.
• cargo clippy --locked -p warp_terminal --all-targets --tests -- -D warnings: passed.
• ./script/format: passed.
• Temporarily removing the image eviction call causes all three replacement regression tests to fail because the old image IDs remain. The fix was restored before running the full crate test suite.

Added regression coverage for:

• Repeated images at the same position, including replacement with a narrower image and the resulting cursor position.

• Preserving images anchored at different rows or columns.

• Preserving Kitty image placements at the same position.

• Preserving the previous image and cursor position when a zero-width replacement is rejected.

• I have manually tested my changes locally with ./script/run

Built the local app with ./script/run --features iterm_images --dont-open and opened the resulting WarpOss.app.

Screenshots / Videos

Before

After

https://github.com/user-attachments/assets/4cc2314d-1ceb-4ad9-837a-dff2b4f93ec2

The before screenshot is from the original Warp recording in #16586. The after screenshots and approximately 18-second Serie recording show the local build based on master commit 1e6c3ae465d6a925a9b97ae03877aaadd159b8f1 with this fix applied.

Agent Mode

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

Changelog Entries for Stable

CHANGELOG-BUG-FIX: Fixed stale inline images remaining visible when applications redraw images using the iTerm2 image protocol.