feat: M4 in-admin manual generation on chained-cron checkpoints + IA/perf pass (v0.21.0) (#166)

Final Phase 2 admin milestone. Board "New Article" runs through the M3 chained-cron checkpoint state machine (one stage/idea per tick, queue persisted before generate, lock released on every exit path) so generation survives Hostinger background-kill; retires the SSH-only do_action workaround (WP-CLI routes through the same entry). IA/perf: settings-backed board/ideas pagination + db 1.4.0 indexes. Folds guard P2s (--self-test + window doc).

QA: APPROVE-WITH-P2-NOTES @ f2a00d4 + delta APPROVE @ 0c8071f. Deferred (tracked): class-admin-page.php 353-line split + pagination Settings-UI fields.

Agent-Session: phase2-admin-m4-20260614

uninstall.php

@@ -97,6 +97,9 @@ $hooks = array(
 	'prautoblogger_opik_dispatch',
 	'prautoblogger_rerun_stage_replay',
 	'prautoblogger_rerun_from_stage',
+	// v0.21.0 (M4): chained-cron checkpoint ticks.
+	'prautoblogger_gen_orchestrate',
+	'prautoblogger_gen_tick',
 );
 
 foreach ( $hooks as $hook ) {