feat(l0): add optional release automation profile pack

[tryingET]

Summary

• add optional enable_release_pack profile toggle (default false) to L0 and nested L2 Copier configs
• add release baseline templates for L1 and L2 sources:
  • workflows: release-please, release-check, publish
  • metadata: .release-please-config.json, .release-please-manifest.json
  • docs: CHANGELOG.md, SECURITY.md
  • scripts: scripts/release/check.sh, scripts/release/publish.sh
• keep defaults conservative by removing release-pack files when enable_release_pack=false
• propagate enable_release_pack into generated .copier-answers.yml and inherit it in L1 scripts/new-repo-from-copier.sh
• extend guardrails/generation/fixture checks and refresh fixtures

Key details

• profile toggles now include:
  • enable_community_pack
  • enable_release_pack
  • enable_vouch_gate
• L0 generation smoke now covers release-enabled case (l1-template-release)
• recursion constraints remain unchanged (L0 -> L1 -> L2; no reverse/cycles)

Validation

• bash ./scripts/check-l0-guardrails.sh ✅
• bash ./scripts/check-l0.sh ✅