BUG-5/BUG-20 fixes: pre_test.sh, output validation, push retry, workflow output tags

- pre_test.sh: harness-level test folder revert script, replaces inline
  _revert_test_folders() in entrypoint. Writes {"reverted": N} atomically.
- finalize.sh: set -x debug tracing; push retry (AGENT_PUSH_RETRIES, default 1
  retry after 5s); output validation (AGENT_EXPECTED_OUTPUT env var); wrong-path
  detection moves .agent-output/ files to working dir and writes
  .correction-prompt.txt for entrypoint re-invoke
- harness.yaml: add scripts.pre_test
- spec-planning.yaml: all 17 nodes tagged with output:{path,min_bytes}

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

harnesses/contexts/agent-repo/v1/harness.yaml

@@ -8,6 +8,7 @@ provides: [project-repo]
 scripts:
   init: "./init.sh"
   finalize: "./finalize.sh"
+  pre_test: "./pre_test.sh"
 
 env:
   AGENT_WORKING_DIR: "/workspace/project"