test(e2e): prove init-scaffolded topology orchestrates and promotes

[joshua-temple]

Problem

The scaffold package's SelfCheck statically proves a cascade init manifest parses, validates, and generates, but nothing proved the scaffolded pipeline actually runs. Static generation cannot catch manifest-shape drift that only surfaces at runtime.

Fix

Adds an e2e scenario (e2e/init_scaffold_test.go) that renders the real two-environment [dev prod] topology via scaffold.Scaffold, unmarshals the live scaffolded manifest's ci.config into the harness Config (so the run is bound to the exact scaffold output, not a hand-copied fixture), and drives it through act and gitea:

• orchestrate after the first commit: build callback runs, version resolves to v0.1.0-rc.0, a draft prerelease is cut at dev
• promote dev to release: v0.1.0 published, rc tag deleted, dev unchanged
• promote release to prod: deploy callback runs, prod state advances

Callback bodies are supplied via SetupWorkflows mirroring the scaffold contract (build emits artifact_id; both take the environment/sha/dry_run inputs) but without actions/checkout, which act cannot resolve for a reusable callback against the per-scenario gitea. This matches the no-checkout pattern the existing runtime scenarios already document and use.

Verification

• Root module: go build ./..., go vet ./..., go test ./... (1345 pass), golangci-lint run ./... clean
• e2e module: go build ./..., go vet ./..., golangci-lint run ./... clean
• Ran the scenario against Docker locally: go test -run TestInitScaffoldOrchestratesAndPromotes -timeout 20m ./... passes (orchestrate + both promotes green, state advances dev -> release -> prod)