fix: add 50MB file size limit to prevent memory spike in editor layout

[warp-dev-github-integration]

Summary

Add a 50MB file size limit to the code editor's file loading path (FileModel::open and FileModel::read_content_for_file) to prevent excessive memory usage when opening very large files.

Root Cause

Sentry alert #7259255054 reports excessive memory usage (17.45GB sampled in heap profile). Analysis of the heap profile reveals:

• SumTree<BlockItem>::push in RenderState::layout_edit_delta — 12.67GB (72.59% of total)
• SumTree<BufferText>::append_str in populate_buffer_with_read_content — 2.08GB (11.94%)
• SumTree<BlockItem>::push_tree / push_tree_recursive — 1.85GB (10.63%)

When a very large file is opened, the entire content is loaded into the buffer, and the editor's layout system creates BlockItem nodes for every line. Since each line generates multiple in-memory structures (text frames, selections, caret positions, etc.), a file that is large on disk can consume 5-10x more memory once fully laid out.

Changes

1. crates/warp_util/src/file.rs: Added FileTooLarge { size_bytes, limit_bytes } variant to FileLoadError
2. crates/warp_files/src/lib.rs: Added MAX_EDITOR_FILE_SIZE (50MB) constant and check_file_size helper. Updated FileModel::open and read_content_for_file to check file size before reading.
3. app/src/ai/blocklist/action_model/execute.rs: Handle new FileTooLarge variant in exhaustive match

Test Plan

• cargo check -p warp_files -p warp_util passes
• Files under 50MB continue to open normally
• Files over 50MB will trigger FileLoadError::FileTooLarge, surfacing through the existing FailedToLoad event path

Follow-up

• Consider adding a user-visible message when a file is rejected for being too large
• Long-term: implement virtual/lazy rendering so the layout system only materializes visible lines

---

Conversation: https://staging.warp.dev/conversation/eed39afb-2a7e-47ef-b94b-b15dcfc91cce
Run: https://oz.staging.warp.dev/runs/019e8484-219d-70b4-9dc3-af3b4d5d9c1c

This PR was generated with Oz.

[kevinchevalier]

Closing as duplicate of #12125 — both add a 50 MB FileTooLarge file size guard in FileModel::open. Keeping the newest PR.