v0.6.1 — ~15x less bd traffic, nix + homebrew packaging

First release since v0.4.0 — v0.5.0 and v0.6.0 were tagged but never published, so their changes are folded in here.

Performance

Steady-state bd traffic per session dropped ~15x. The channel poll now issues one bd query per pass instead of four, and backs off from 15s to a 60s ceiling while idle; the heartbeat is down to 3 bd calls per 60s bucket. Measured on an idle registered session: ~3.6 bd calls/min, down from ~65.

Delivery errors are also caught per session rather than around the whole sweep — one slow bd call no longer aborts delivery for every other session in that pass.

Packaging

• Nix flake — nix run github:zach-source/claude-mailbox.
• Homebrew tap — brew install zach-source/claude-mailbox/claude-mailbox.
• The beads workspace now resolves per-user to ${XDG_DATA_HOME:-~/.local/share}/claude-mailbox (override with MAILBOX_WORKSPACE). Earlier builds resolved it to <prefix>/lib/pythonX.Y, which no installed build could write to — installed builds before v0.6.0 do not work.
• MIT LICENSE now ships in the release tarball. v0.6.0's tarball was cut before the license landed, which is the only reason this is 0.6.1.

Upgrade

No config changes. If you installed from a pre-0.6.0 tag, initialize the workspace once:

mkdir -p ~/.local/share/claude-mailbox
bd init -C ~/.local/share/claude-mailbox
bd init --global