feat(dag): add proactive composable routing

[LeXwDeX]

Summary

• proactively route project-level implementation and repository-backed product/architecture work through DAG orchestration without requiring /dag-flow
• keep the parent session responsible for decisions, recommended answers, one combined confirmation, and final reporting
• add composable explore, plan, prototype, debug, coding, verify, review, and synthesize blocks with durable-node compilation and legacy node compatibility
• move detailed routing, policy, pattern, and block guidance behind progressive workflow(action: "guide") disclosure
• make review a two-lane standards/intent check with a structured verdict gate

Prompt impact

• always-on workflow context: about 58.8k characters -> about 2.8k characters
• /dag-flow prompt: about 66k characters -> about 2.0k characters

Validation

• bun typecheck in packages/core
• bun typecheck in packages/opencode
• 85 focused tests passed across core command/skill and DAG workflow/block coverage
• pre-push whole-repository typecheck: 29/29 packages passed
• git diff --check

Companion templates: opencode-dag-config#1. Merge this runtime PR before releasing the templates.