refactor(extensions): centralize session ownership

[benvinegar]

Summary

• add a renderer-independent ExtensionSession as the sole owner of active, provisional, adopted, retiring, and closing extension registries
• preserve extension startup and reload events behind AppHost's matching React layout commit
• make standalone review, interactive history, static history, and embedded reviews use explicit session ownership
• require embedded history reviews to borrow the current registry and reject independently owned nested authority
• preserve provider cursor → extension shutdown → renderer teardown ordering across success and failure paths
• add lifecycle-aware AppHost helpers for tests and benchmarks

Validation

• 2,008 unit tests passed; 9 skipped
• 150 PTY integration tests passed; 1 platform skip
• 9 TTY smoke tests passed
• bun run typecheck
• bun run lint
• bun run deps:check
• bun test scripts/source-boundaries.test.ts
• bun run check:docs
• git diff --check
• independent lifecycle and architecture review found no blockers

Stack

1. refactor(ui): route surfaces through one session runtime #998 — shared session runtime and surface router
2. refactor(extensions): centralize session ownership #999 — centralized extension session ownership

This PR description was generated by Pi using gpt-5.6-sol

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1 Skipped Deployment

Project	Deployment	Actions	Updated
hunk-web	Ignored	Preview	Sep 6, 2026 1:03pm UTC

[greptile-apps]

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