refactor: DRY monitor action render wrapper

[somethingwithproof]

Problem

monitor.php repeats action-handling flow where several actions perform one operation and immediately render the page.

Proposed change

• add a shared action wrapper helper to run an action callback and render monitor output
• route repeated render-after-action branches through this helper
• preserve behavior

Tests

• add standalone regression test for helper call order
• add source assertions that repeated action branches use helper
• run syntax checks for touched files