Bound local Code editor file reads

[warp-agent-staging]

Description

Bounds local Code editor reads to 100 MiB before full string or editor-buffer materialization, preventing oversized files from amplifying memory use across Code Editor and Code Review. The guard covers initial opens, direct rereads, and watcher reloads; exact-limit files retain existing behavior, while oversized loads show a limit-aware error instead of an empty editor. Subscribed oversized files remain watched and automatically populate the editor after shrinking below the limit.

Linked Issue

APP-4844

Testing

• ./script/format --check
• cargo nextest run -p warp_files --no-fail-fast — 39 passed
• cargo nextest run -p warp -E 'test(/file_load_error_message|oversized_content_is_rejected_before_initial_and_fallback_population/)' --no-fail-fast — 3 passed
• cargo test -p warp --lib code_review::code_review_view::tests --no-fail-fast — 18 passed
• cargo build -p warp --lib
• Presubmit clippy matrix from script/presubmit — passed
• cargo clippy --workspace --all-targets --all-features --tests -- -D warnings — blocked by existing incompatible feature-gated execution-profile tests and unrelated dead-code errors; script/presubmit explicitly omits --all-features
• I have manually tested my changes locally with ./script/run (computer-use verification was closed for this implementation)

Agent Mode

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

CHANGELOG-BUG-FIX: Prevented oversized local files from exhausting memory when opened in Code Editor or Code Review.

ticket_source=linear
ticket_id=APP-4844

[warp-agent-staging]

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