chore: drop .github/ — this repo is a read-only mirror

Contributions land in the upstream private tracker, not here.
Removing .github avoids confusing contributors into opening PRs
against a mirror that never merges directly.

.github/pull_request_template.md

@@ -1,11 +0,0 @@
-## Dream v2 PR Checklist
-
-- [ ] Only modifies current Phase scope; no future Phase undecided designs introduced
-- [ ] Feature flag defaults to off
-- [ ] `scripts/rfc-lint.sh` passes locally
-- [ ] New Flyway migrations exist in both h2/ and mysql/ directories
-- [ ] New `@Scheduled` cron expressions documented in application.yml with stagger rationale
-- [ ] Phase 1 PR: `recall_count / daily_count` regression test passes
-- [ ] Phase 3 PR: `mate_fact` two-write-path SQL-level guard test passes
-
-Related RFC: <!-- rfc-035 P1-S{x} / rfc-037 P1-S{x} / ... -->