test: verify multi-handler ordering with reverted ExternalActionPlugin

[shahabdsh]

Summary

Companion to #838. This PR reverts #832 (ExternalActionPlugin refactor) and adds the same multi-handler ordering tests to demonstrate that all 3 tests pass with the pre-refactor implementation.

What this PR contains

1. Revert of Refactor external action plugin #832 — restores the transition hook + setTimeout(0) implementation
2. Same test file as test: multi-handler ordering regression in ExternalActionPlugin #838 — 3 tests for multi-handler ordering behavior

Why the tests pass here but fail on main

With the original setTimeout(0) approach:

• Each handler runs in its own deferred microtask
• If the first handler resolves synchronously, it transitions within its setTimeout callback
• The second handler's setTimeout callback finds the player has already moved away from the external state → second handler is never invoked

With the afterTransition approach (#832):

• Both handlers fire synchronously on the same hook call
• Both capture currentState at the same moment, before either transitions
• Both handlers are always invoked, even if the first one resolves synchronously

This behavioral difference affects plugin architectures where multiple ExternalActionPlugin instances are registered — the second handler's side effects now fire even when the first handler has already resolved the external state.

Test results

PR	Test 1 (sync)	Test 2 (async race)	Test 3 (delegate)
#838 (main)	FAIL	PASS	PASS
This PR (reverted)	PASS	PASS	PASS

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