perf(app): defer the closed workbench panel

[Itsnotaka]

Summary

• defer the closed workbench panel column until it opens or owns a managed tab
• defer Browser and Terminal runtime panes behind exact shared-layout fallbacks
• add a dev startup guard and a written performance/first-paint review

Performance

• eager app source: 1,333.2 KiB -> 1,256.5 KiB (-5.75%)
• median Electron process-to-ready: 6,325 ms -> 5,940 ms (-6.09%)
• median window-created-to-ready: 5,495 ms -> 5,110 ms (-7.01%)
• median initial React render: 2.0 ms -> 1.8 ms (no regression)
• median commit-to-next-frame: 5.8 ms -> 5.4 ms

Measurements used one warm-up and three interleaved dev runs per tree. Temporary profiler probes were removed.

Verification

• 33 focused app tests pass
• app production build passes
• startup graph guard passes
• targeted Oxlint and formatting pass
• React Doctor: only pre-existing maintainability warnings
• app typecheck: inherited onboarding-layout.tsx gearColossus error only
• repo architecture/design: inherited oversized-file and v2.tsx violations only

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Project	Deployment	Actions	Updated (UTC)
honk-marketing	Ready	Preview	Aug 4, 2026 6:30pm