Implement fleet-to-fleet combat logic for Ork fleets

[coderabbitai]

Description

A TODO marker exists in scripts/scr_ork_fleet_functions/scr_ork_fleet_functions.gml (line 155) noting the need to provide logic for fleets to attack each other.

Currently, the merge_ork_fleets() function handles merging multiple Ork fleets at the same star system, but there is no combat resolution when opposing faction fleets encounter one another.

Requirements

• Implement fleet-to-fleet combat logic when Ork fleets encounter enemy fleets
• Determine combat resolution mechanics (ship losses, retreat conditions, etc.)
• Consider interactions between different fleet types (capital ships vs frigates)
• Ensure compatibility with existing fleet movement and merge systems

Acceptance Criteria

• Ork fleets can engage enemy fleets in combat
• Combat results affect fleet composition (capital_number, frigate_number)
• Combat outcomes are logged appropriately
• Fleet behaviour after combat is defined (retreat, pursue, occupy, etc.)

Context

• Related PR: feat: WAAAAGH flavor text changes #1063
• Discussion: feat: WAAAAGH flavor text changes #1063 (comment)
• Requested by: @Blogaugis

Location

File: scripts/scr_ork_fleet_functions/scr_ork_fleet_functions.gml
Line: 155