v1.5.1

register recreates missing project channels

The maintenance tick drops an empty channel that no live session subscribes
to. The general/<repo>, memory/<repo>, and tasks/<repo> channels that
agentbus init creates could therefore be gone before the first session
registered, and register reported them in subscribe_failed as
does not exist. register now creates every prefixed channel listed in
.local/agentbus.json before subscribing to it. A channel without a
general/, memory/, or tasks/ prefix still needs create_channel.

Upgrading from before v1.5.0

Restart every harness session and the TUI after brew upgrade agentbus. An
agentbus mcp process still running a pre-1.5.0 binary deletes the default
tasks channel and every empty tasks/<repo> list on each tick, because
its reaper does not know tasks is a default. Once no old process remains,
the next register in each repository brings the channels back.