perf(app): defer the inactive thread route

[Itsnotaka]

What changed

• load ThreadPage through one cached dynamic import
• start that import from the thread route's beforeLoad hook
• keep Home from requesting transcript, Markdown, composer, tray, tool, and subagent code
• share the existing connecting frame between the real page and Suspense fallback
• guard the thread page out of Home's static startup graph

Why

Home could not use 39 modules pulled in by the static ThreadPage import, but every Home launch parsed them.

Measured result

• eager app source: 1,205.2 to 897.1 KiB, down 25.6%
• initial JavaScript: 2,731,288 to 1,582,460 bytes, down 42.1%
• initial gzip: 832,684 to 494,276 bytes, down 40.6%
• Electron process-to-ready median: 6,449 to 5,125 ms, down 20.5%
• Electron window-ready median: 5,582 to 4,301 ms, down 23.0%
• first-frame renderer heap median: 115.16 to 98.75 MiB, down 14.3%
• React initial render median: 2.2 to 2.1 ms
• commit-to-next-frame median: 3.8 to 4.5 ms

Verification

• pnpm --filter @honk/app dev:startup-review failed on thread/page.tsx before the split, then passed and started Vite
• 11 focused thread route, session layout, and tab controller tests pass
• exact server-rendered connecting markup is locked by a focused test
• repeated route preload calls are verified to share one import promise
• pnpm --filter @honk/app build
• focused oxfmt, oxlint, and diff checks
• React Doctor reports no issue in an improvement-8 file

Repository-wide typecheck remains blocked by the same onboarding-layout.tsx:344 gearColossus error on both trees. Design lint reports only the 12 legacy /v2 findings already on main. The architecture check still reports the same five pre-existing oversized files.

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Project	Deployment	Actions	Updated (UTC)
honk-marketing	Ready	Preview	Aug 4, 2026 7:30pm