refactor: optimize action Execute() allocations using collection expressions

[mcj-coder]

Context

Actions are executed in hot paths (potentially hundreds of NPCs per tick). Current implementation allocates a new List<IGameEvent> on every execution.

Current Implementation

public IReadOnlyList<IGameEvent> Execute(...)
{
    var events = new List<IGameEvent>();  // Allocation on every call
    // ...
    return events;
}

Proposed Solution

Use C# 12 collection expressions for zero-allocation fixed-size collections:

// RestAction (2 events)
return [
    new NeedChangedEvent(...),
    new NeedChangedEvent(...)
];

// EatAction (1 event)
return [new NeedChangedEvent(...)];

Benefits

• Zero allocation for single-element collections
• Minimal allocation for fixed-size collections
• More readable and concise
• Better performance in hot paths

Files to Update

• src/FantasyRpgWorld.Core/Actions/RestAction.cs
• src/FantasyRpgWorld.Core/Actions/EatAction.cs
• src/FantasyRpgWorld.Core/Actions/WorkAction.cs

Acceptance Criteria

• All three actions use collection expressions
• All existing tests pass
• Zero warnings build

Related

Identified in PR #112 review by .NET Specialist
Part of Epic 3: NPC Decision Making

Labels

• type:refactor
• priority:medium
• area:performance