fix(Scripts/HoR): clear IMMUNE_TO_PC before engaging Falric and Marwyn

[Nyeriah]

Changes Proposed:

This PR proposes changes to:

• Core (units, players, creatures, game systems).
• Scripts (bosses, spell scripts, creature scripts).
• Database (SAI, creatures, etc).

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Issues Addressed:

• Closes In Halls of Reflection (Heroic), the first boss does not engage and remains inactive. #25259

Description:

Same root cause as #25263 — after the TrinityCore heap-based threat system port (#24715) and the removal of auto-immunity-clearing in Creature::AtEngage (#25121), creatures with IMMUNE_TO_PC (0x100) in their creature_template.unit_flags that don't explicitly clear it before entering combat are broken.

Both Falric (38112) and Marwyn (38113) have unit_flags = 832 which includes IMMUNE_TO_PC. Their scripts call SetImmuneToAll(false) inside JustEngagedWith(), but by that point ThreatReference::FlagsAllowFighting() has already returned false for all threat references created during SetInCombatWithZone(), marking them as OFFLINE. This causes UpdateVictim() to return nullptr, so the bosses appear to never engage.

Fix: Add SetImmuneToPC(false) before SetInCombatWithZone() in the delayed combat start lambda for both Falric and Marwyn, ensuring threat references are created with proper flags.

SOURCE:

The changes have been validated through:

• Video evidence, knowledge databases or other public sources (e.g forums, Wowhead, etc.)

Source code analysis of ThreatManager.cpp (FlagsAllowFighting, ShouldBeOffline) confirming the interaction between IMMUNE_TO_PC and the new threat reference system. Same pattern as #25263.

Tests Performed:

This PR has been:

• Tested in-game by the author.
• Tested in-game by other community members/someone else other than the author/has been live on production servers.
• This pull request requires further testing and may have edge cases to be tested.

How to Test the Changes:

• This pull request can be tested by following the reproduction steps provided in the linked issue
• This pull request requires further testing. Provide steps to test your changes. If it requires any specific setup e.g multiple players please specify it as well.

1. Enter Halls of Reflection (Normal or Heroic)
2. Complete the intro event and clear all 5 waves
3. Verify Falric says his aggro line and engages in combat after ~8 seconds
4. Kill Falric, clear waves 6-10
5. Verify Marwyn similarly engages after his aggro line

Known Issues and TODO List:

• Verify wipe/resume behavior still works correctly after the fix
• Regression test Marwyn (wave 10) engagement

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[Copilot]

Pull request overview

Fixes Halls of Reflection boss engagement after the threat-system changes by ensuring UNIT_FLAG_IMMUNE_TO_PC is cleared before SetInCombatWithZone() creates threat references, allowing Falric and Marwyn to properly acquire a victim and start their AI.

Changes:

• Clear IMMUNE_TO_PC right before delayed SetInCombatWithZone() for Falric.
• Clear IMMUNE_TO_PC right before delayed SetInCombatWithZone() for Marwyn.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/server/scripts/Northrend/FrozenHalls/HallsOfReflection/boss_falric.cpp	Clears PC-immunity before forcing zone combat so threat refs aren’t created OFFLINE.
src/server/scripts/Northrend/FrozenHalls/HallsOfReflection/boss_marwyn.cpp	Same fix for Marwyn’s delayed combat start path.

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