feat: add composable workflow routes

[LeXwDeX]

Summary

• convert the change-review template from hand-written durable nodes to composable workflow blocks
• add project-change, debug-repair, product-decision, and prototype-decision routes
• keep parent-session decision ownership explicit: routes surface evidence and recommendations, while the parent asks for one combined confirmation
• encode reusable exploration, planning, coding, verification, review, and synthesis contracts without external runtime dependencies

Compatibility

This PR uses the block interface introduced by OpenCode-GraphAgent#223. Merge and release the runtime PR before releasing these templates. Existing low-level node templates remain compatible.

Validation

• all 16 YAML templates decode against the runtime StartSpec
• every block template compiles into a valid durable DAG
• git diff --check