Add island_members variable to level formula for team-size handicap support

[Copilot]

Multi-member islands have an inherent advantage over solo players since more members means more blocks placed. Admins had no way to normalize level by team size.

Changes

• IslandLevelCalculator: Resolves island_members placeholder in the level-calc formula to the island's current member count before equation evaluation. Uses Math.max(1, memberCount) to guard against division-by-zero on unowned islands. Also added member count to the level calculation report output.
• ConfigSettings: Updated level-calc config comments to document island_members and provide a handicap example.
• README.md: Added formula variables reference table and handicap usage example.

Example

To normalize island level by team size, set in config.yml:

level-calc: "blocks / level_cost / island_members"

With level_cost: 100, a block worth 100 points yields:

• Solo island (1 member): level contribution = 100 / 100 / 1 = 1.0
• 3-member island: 100 / 100 / 3 ≈ 0.33
• 4-member island: 100 / 100 / 4 = 0.25

The default formula (blocks / level_cost) is unchanged — island_members is only substituted if present in the formula string.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud