feat(M3): re-run engine — replay + rebuild as chained-cron jobs under CPO guardrails

Two operator primitives, both queued (never synchronous — CPO hard
constraint), all mutations in the cron handler after re-validating
eligibility UNDER the generation lock:

- Replay (Stage_Replay + on_replay_job): one governed chat call from the
  latest edited input fork. options_from_body() is the exact inverse of
  build_body()+apply_reasoning_budget() (headroom subtracted back out;
  reasoning pinned explicitly so global-setting drift can't reshape a
  replay). Goes through send_chat_completion -> cost governor reserves
  against the SAME run row (guardrail 4), retry/empty-guard machinery,
  B1 recorder. Fresh output lands in the stage snapshot; downstream
  stale-marked (guardrail 3); human_modified set at execution entry
  (guardrail 2).
- Rebuild (on_rebuild_job): demote target+downstream to pending, re-enter
  Article_Worker with the idea from the stored seed; upstream done stages
  reuse (never re-charged), demoted stages rebuild prompts from CURRENT
  snapshots — how an upstream edit propagates. Decisions recorded while
  rebuilding a human-modified item are flagged.
- Rerun_Eligibility: published/future/private = frozen (guardrail 5,
  server-side); executing runs blocked; editable stages = writer chat
  stages (outline/draft/polish); chain-order downstream sets.
- Run_State::reopen(): atomic terminal->running gate, ceiling
  re-snapshotted from the current setting, accumulated spend NEVER reset.
- Publisher: re-run output refreshes the existing UNPUBLISHED post
  (status preserved — re-runs never publish); published posts untouched.
- Article_Worker persists the exact idea payload as a seed (INSERT-once)
  so rebuilds can't mis-derive item_key and duplicate a post.
- Rerun_Job_Support: queue/lock/budget/status-transient plumbing; jobs
  ride the M1 status transient so the board shows queued->pickup->result.

Agent-Session: engineer-prab-m3-20260612

includes/core/class-article-worker.php

@@ -58,6 +58,13 @@ class PRAutoBlogger_Article_Worker {
 		$run_id = (string) ( $this->cost_tracker->get_run_id() ?? '' );
 		$item   = PRAutoBlogger_Run_Stage_State::item_key_for_idea( $idea );
 
+		// v0.20.0: persist the EXACT idea payload once per item so
+		// re-run-from-here can reconstruct it (rebuilding from post
+		// fields would risk an item_key hash mismatch -> duplicate post).
+		if ( '' !== $run_id ) {
+			PRAutoBlogger_Stage_Input_Store::save_seed( $run_id, $item, (string) wp_json_encode( $idea->to_array() ) );
+		}
+
 		$result = array(
 			'generated' => 0,
 			'published' => 0,