GitHub Issues as the default tracker

Decided: ADR-010 - free and unlimited wins for the default; Jira and Linear as adapters behind one one-way bridge.

Doubt: GitHub Issues is the weakest PO experience of the three; Linear's free cap (250 active issues) may bite mid-project; the bridge convention is field-proven against Jira only.

A better answer would: evidence from a second bridge implementation, or a default that serves POs better at zero cost.