fix: prevent multi-GiB memory spikes in editor for large files (APP-4519)

[warp-dev-github-integration]

Description

Prevent multi-GiB memory spikes when loading very large files into the code editor. The Sentry memory alert (APP-4519) shows 24+ GiB heap usage dominated by SumTree<BlockItem>::push (82.5%) and SumTree<BufferText>::append_str (13.7%) after a GlobalBufferModel file load.

This PR implements three defensive layers:

1. File size guard (20 MB) — FileModel and GlobalBufferModel reject files exceeding MAX_EDITOR_FILE_SIZE before reading content into the buffer. Applies to local files, remote buffers, and auto-reload paths. A user-friendly toast shows the file size and the limit.

2. Lightweight layout (5 MiB threshold) — When an EditDelta's total content exceeds MAX_LAYOUT_BYTES, layout_text_block_lightweight creates empty TextFrames with correct font metrics instead of running expensive platform text layout (CoreText on macOS). This prevents the 19+ GiB SumTree<BlockItem> retention seen in the Sentry heap profile.

3. Tree-sitter guard (1 MiB) — Buffers exceeding MAX_SYNTAX_TREE_BUFFER_BYTES skip tree-sitter parsing entirely, avoiding multi-GiB heap spikes from grammars with expensive external scanners.

Also removes an unnecessary .clone() on EditDelta in DelayRendering::flush_render.

Files changed

• crates/warp_util/src/file.rs — Add MAX_EDITOR_FILE_SIZE constant and FileTooLarge error variant
• crates/warp_files/src/lib.rs — File size check before reading in open(), read_content_for_file(), and auto-reload
• app/src/code/global_buffer_model.rs — Remote buffer size guard in apply_open_buffer_response
• app/src/code/view.rs — User-friendly toast for file-too-large errors
• app/src/ai/blocklist/action_model/execute.rs — Handle FileTooLarge error variant
• crates/editor/src/content/buffer.rs — Add byte_len() and content_byte_len() helpers
• crates/editor/src/content/edit.rs — Add MAX_LAYOUT_BYTES, layout_text_block_lightweight, and lightweight layout dispatch
• crates/syntax_tree/src/lib.rs — Add MAX_SYNTAX_TREE_BUFFER_BYTES guard
• app/src/code/editor/model.rs — Remove unnecessary .clone() on EditDelta

Linked Issue

• Linear: APP-4519
• Sentry: https://warpdotdev.sentry.io/issues/7259255054/

Testing

• cargo fmt — passes

• cargo clippy --workspace --all-targets --all-features --tests -- -D warnings — passes

• This change addresses the root cause of the Sentry memory alert by preventing large file content from entering the editor pipeline

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

Conversation: https://staging.warp.dev/conversation/84b4c4e8-93a6-4ca5-8773-4a7454f2224d
Run: https://oz.staging.warp.dev/runs/019e4450-ddfc-7a01-8ca0-2d3f07b81511
This PR was generated with Oz.