chore(repo): add CODEOWNERS for runtime ABI, CI, and release tooling

@clerk/team-sdk owns the hotload-boundary runtime surface that ships to consumer
apps without version bumps (clerk-js core clerk.ts, react isomorphicClerk, ui
contexts), plus the CI workflows, the CODEOWNERS policy itself, and the changeset
config/changelog. Per-PR changeset entries are left unowned so they don't gate
every PR. Empty changeset (repo-level config).

Author: jacekradko

.changeset/codeowners-hotload-boundary.md

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+---
+---

.github/CODEOWNERS

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+# Hotload boundary
+#
+# These files are part of the runtime surface that ships to consumer
+# apps without explicit version bumps. See AGENTS.md for context.
+
+/packages/clerk-js/src/core/clerk.ts          @clerk/team-sdk
+/packages/react/src/isomorphicClerk.ts        @clerk/team-sdk
+/packages/ui/src/contexts/                    @clerk/team-sdk
+
+# CI workflows and repo automation
+#
+# Changes here affect how every PR is built, gated, and merged, and the
+# CODEOWNERS policy itself.
+
+/.github/workflows/                           @clerk/team-sdk
+/.github/CODEOWNERS                            @clerk/team-sdk
+
+# Release tooling
+#
+# Changeset config and changelog generation drive what gets published and
+# how versions are computed. The per-PR changeset entries (.changeset/*.md)
+# are intentionally left unowned so they don't gate every PR.
+
+/.changeset/config.json                       @clerk/team-sdk
+/.changeset/changelog.js                      @clerk/team-sdk