chore: drop upstream gsd issue and pr governance

MSD does not use an issue tracker, and the inherited GSD community gates
auto-closed PR #1 for lacking an issue-numbered title. Remove them:

- workflows: require-issue-link, pr-title-validator,
  auto-close-unsolicited-prs, pr-template-format, close-draft-prs(-sweep),
  auto-label-issues, auto-branch, duplicate-check, duplicate-sweep,
  remove-duplicate-label
- GSD PR and issue templates, plus the scripts only they used
  (require-issue-link-policy, pr-template-policy, pr-changed-files) and
  their tests
- workflow lists in ci-test-scope, ci-pr-mergeability,
  workflow-maintainer-skip, lint-pr-check-project-dir, the docs-guard
  baseline and the conformance tiers
- CONTRIBUTING: PR-against-next flow with no issue or template; PR titles
  are conventional without an issue ref; ADR/PRD files use the PR number
- CONTEXT.md: drop the PR-template predicates (k328, templates-mandatory)

scripts/ci-test-scope.cjs

@@ -17,14 +17,9 @@ const INERT_WORKFLOWS = new Set([
   'stale.yml',
   'branch-cleanup.yml',
   'branch-naming.yml',
-  'auto-label-issues.yml',
-  'auto-branch.yml',
   'auto-backmerge.yml',
-  'close-draft-prs.yml',
   'dismiss-unauthorized-pr-approvals.yml',
   'pr-target-validator.yml',
-  'pr-template-format.yml',
-  'require-issue-link.yml',
   'changeset-required.yml',
   'docs-required.yml',
   'discord-changelog.yml',
@@ -65,7 +60,6 @@ function isInertCi(filePath) {
 // Tests shared by both the 'workflow automation' and 'inert CI' rules.
 const WORKFLOW_LINT_TESTS = [
   'tests/workflow-shell-pinning.test.cjs',
-  'tests/pr-template-policy.test.cjs',
   'tests/lint-pr-check-project-dir.test.cjs',
 ];