refactor(cli): rewrite CLI package for improved observability and error tracing

Author: eluce2

.changeset/proofkit-cli-major-migration.md

@@ -2,11 +2,4 @@
 "@proofkit/cli": major
 ---
 
-Promote the rewritten Effect CLI as the public `proofkit` binary and restore the publishable scaffold/manage flow for the beta major release.
-
-This release:
-
-- switches the public binary name from `proofkit-new` back to `proofkit`
-- records generated scaffold metadata against `@proofkit/cli`
-- restores the template assets and legacy project-management command surface inside the new CLI package
-- keeps the old `cli-old` package internal so workspace filters and release tooling only target the new CLI
+Rewrite the CLI package for better observability, composability, and error tracing.