[mirror] Upstream PR: lazy widget editors (undici out of render path)

[axisrow]

Tracker for the lazy-widget-editors follow-up (extends upstream 35440e4, their sirmalloc#575 "keep the TUI off the status line render path").

Status in our fork: DONE. Merged as PR #3 (rebased onto main after PRs #1/#2, deduped, CI green).

What landed:

• The eleven widget-editor implementations moved into lazy chunks (React lazy/Suspense) preserving the synchronous renderEditor API; render-time widget logic unchanged.
• Built no-proxy piped render now records 0 fetches, 0 WASM initializations, no undici (vs 1/1/loaded before) — the eager editor → Ink useInput → reconciler → Yoga route no longer executes on render.
• CPU per render: −7.7% (Node) / −12.7% (Bun) vs PR perf: reduce per-repaint CPU under concurrent sessions #2 head; Node p50 −1.8% disclosed.
• Editor first-open can suspend briefly (~300 ms).
• Artifacts on main: docs/performance-397-verification.md, docs/performance-397-results.json, scripts/benchmark-render.py.

Next step: upstream PR building on their sirmalloc#575 work — pending user go.

[axisrow]

Fork-side work is done: lazy widget editors with undici out of the render path are in fork main (src/widgets/shared/lazy-editor.tsx, src/widgets/editors/*). Closing.