feat(pr): add review thread replies and resolution

[danielss-dev]

Summary

• add provider-neutral review-thread reply and resolve/reopen IPC contracts
• implement GitHub GraphQL mutations with fail-closed viewer capabilities and stdin payloads
• patch inline thread cards and Conversation locally with persistent drafts, keyboard controls, and ARIA feedback
• update project tracking, documentation, and durable thread-ID guidance

Test plan

• cargo test -p strand-tauri pull_requests
• cargo check -p strand-core -p strand-tauri
• pnpm --filter ./ui test
• pnpm --filter ./ui exec tsc --noEmit
• pnpm --filter ./ui exec vite build
• isolated Tauri/CDP verification with seeded thread data at normal and narrow widths in light and dark themes; no hosted comments published