Stabilize opencode host dir test env

fix(runner): serialize mounts_test with mount_state_test

TestLaunchCommandsUseSplitMounts was racing with tests in
mount_state_test.go because both modify the package-level runCommand
and commandOutput variables. Add mountStateTestMu lock to serialize
these tests.

Handle case-insensitive 'no such object' errors from docker

build(mac-leash): bump version to 1.1.0

build: publish docker images to ECR public