DevCake v0.6.3

Patch release in the v0.6 "Kentucky Butter" line. devcake-cli stays at 0.1.8.

A mission that cannot start is now visible. A mission whose dispatch DevCake refuses or defers for a reason a person can act on, for longer than a threshold (thirty minutes by default), is listed on the health endpoint with its age, raised as an alert on the admin Overview, and badged on its board card. The ticket receives one notice per distinct block, and its status comment is created early with a "waiting to start since" line that says why and what would clear it. Waiting on a blocker never counts, the same block is never repeated, a different block notifies again, and neither the notice nor the status comment ever enters a Dev's context. The occasion was a decomposition child that sat for eight days after its original was archived, with only a log line saying so.

Upgrading a host.

devcake up --release

Full detail: CHANGELOG.md and the living log in docs/16-roadmap.md.