[FEAT] Add forProject() scoped bus channels to BusClient and BusTui

[four-bytes-robby]

Purpose

Complete the project-scoped bus API by adding forProject(id) to both BusClient and BusTui.

What's missing

forService and forSession exist but forProject was planned and marked done without being implemented.

Changes

• BusClient.forProject(id) + ScopedBusClient.forProject(id) — prefix-based, same mechanics as forSession
• BusTui.forProject(id) + ScopedBusTui.forProject(id) — same

Channels: brain/{projectId}/status (project-level) vs brain/{sessionId}/status (session-level).

Used by four-opencode-brain to publish startup/ingest status to a project-scoped channel so all sessions in the project receive it via useProjectBus.

[coderabbitai]

🔗 Related PRs

#9 - feat: add forService/forSession scoped bus API #8 [merged]
#11 - fix: scoped bus close() tears down shared bus (P1) #10 [merged]
#14 - fix: MemoryBusTui never upgrades + spawn lock #13 [closed]

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