v1.7.20

Changelog

• 979d420 Revert "feat(opencode): add model field to SDD agent configs"
• a6257a5 feat(opencode): add model field to SDD agent configs
• 9ba60bb refactor(opencode): align single overlay with multi subagent structure
• 84bedd6 test(e2e): rename single mode test to reflect subagent structure
• aa999b0 test(e2e): update SDD single mode assertions for subagent structure
• 9f43b9c test(sdd): update tests for single overlay subagent structure