Reduce Codex presentation support work

[VolkerChristian]

Summary

• target sidebar and Inspector updates to affected threads, selections, and linked agents
• bound accumulated presentation refresh identities and degrade safely to a full refresh
• prepare attachments asynchronously with cooperative cancellation and lifetime-safe result delivery
• avoid broad conversation work for exact streaming content updates

Validation

• full restacked CodexUI suite passes 7/7 locally against installed AISuite master
• renderer-base exact-current live stream handled 271 appends with exactly one visible paint per append at the original 16 ms cadence
• live synchronization and backend-only reconnect testing pass without frontend restart, write backlog, or idle CPU load
• renderer-base regressions cover visible-document measurement isolation, atomic geometry settlement, stable active-turn streaming, and one terminal Markdown promotion

Stack

• base PR: Render Codex conversations incrementally #36
• worker base PR: Move Codex frontend processing off the UI thread #35
• AISuite dependency: Publish Codex frontend state incrementally AISuite#48, merged