feat: add research discovery flow

[dapi]

What changed

• adds the governed Research & Discovery flow and R-XXX templates
• defines research lifecycle ownership, evidence provenance, and downstream handoff rules
• validates research package lifecycle gates, artifact status, and required package index
• updates template ownership and the dependency map

Why

Research needed a governed path before delivery decisions, with doctor checks that prevent invalid lifecycle states.

Validation

• memory-bank lint
• go test -count=1 -race ./...
• go vet ./...
• git diff --check