Briar v1.2.89

What's Changed

• fix(agent): make saved responsibility an execution objective by @siisee11 in #773
• docs: publish v1.2.88 changelog by @siisee11 in #774
• fix(agent): align session status with structured outcome by @siisee11 in #775
• feat: release iOS TestFlight 1.2.88 build 1 by @siisee11 in #776
• chore: release v1.2.89 by @siisee11 in #777

Full Changelog: v1.2.88...v1.2.89