Fix zones not recovering after heightmap edit in Risk mode

[Copilot]

Description

Zones were lost after heightmap editing in Risk mode due to incorrect DOM selector. Code attempted to backup/restore zones via zones.selectAll("g"), but zones render as <path> elements, causing the logic to never execute.

Changes:

• Replace SVG DOM manipulation with direct pack.zones array operations
• Before reGraph(): store zone→gridCells mapping in local zoneGridCellsMap (Map) - avoids mutating zone objects
• After reGraph(): create gridToPackMap for O(1) lookups, restore zones using flatMap
• All temporary data stored in local variables - no pollution of zone objects
• Remove all inline comments for cleaner code
• Update version to 1.112.2 and cache hash for heightmap-editor.js

Result: Zones now persist correctly through significant graph changes (coastline modifications, etc.)

Performance Optimization:

• Original implementation: O(n²) complexity with filter and includes
• Optimized implementation: O(n) complexity using Map for constant-time lookups
• Creates grid→pack cell mapping once, then uses flatMap for efficient zone restoration

Data Safety:

• Original approach mutated zone objects with temporary zone.gridCells property
• New approach uses local Map to store zone→gridCells mappings
• Prevents accidental serialization of temporary data in saves
• Prevents schema collisions
• No cleanup needed - temporary Map is garbage collected automatically

Code Quality:

• Before: 27 lines of non-functional DOM manipulation
• After optimization & cleanup: 11 lines of efficient, safe data model operations

Screenshots

Zones displayed before heightmap edit:

Zones successfully restored after heightmap edit:

Type of change

• Bug fix
• New feature
• Refactoring / style
• Documentation update / chore
• Other (please describe)

Versioning

• Version is updated
• Changed files hash is updated

Original prompt

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This section details on the original issue you should resolve

<issue_title>Risk Heightmap Edit: Zones are not recovering after significant change</issue_title>
<issue_description>Heightmap Edit in Risk, with significant graph change, causes zones to be incorrect.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Risk Heightmap Edit: Zones are not recovering after significant change #1326

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[Copilot]

Pull request overview

Fixes Risk-mode heightmap editing so zones survive significant reGraph() changes by persisting zone membership via the data model instead of broken SVG DOM selection logic.

Changes:

• Backup zones using pack.zones[*].cells -> grid cell ids before reGraph()
• Restore zones by mapping saved grid cell ids back onto new pack cells after reGraph()
• Remove prior (non-functional) SVG DOM-based backup/restore logic