chore(legacy JSON): migrate all 8 files from JSON.new().parse() to JSON.parse_string()

[niyazmft]

Summary

Eight .gd files use the legacy Godot 3.x pattern JSON.new().parse(text) instead of the Godot 4.x idiomatic JSON.parse_string(text). This is inconsistent with scripts/autoload/config_loader.gd:139 which already uses the modern pattern.

Files Affected

File	Lines
scripts/combat/room_loader.gd	29-30
scripts/core/encounter_system.gd	55-56
scripts/core/loot_table.gd	29-30
scripts/core/room_generator.gd	86-87
scripts/autoload/settings_manager.gd	75-76
scripts/autoload/grid_system.gd	166-167
scripts/autoload/save_manager.gd	131-132
scripts/entities/apparition_renderer.gd	124-125

Suggested Fix

Replace:

var json := JSON.new()
var err := json.parse(text)
if err != OK:
    push_error("...")
    return {}
return json.data

With:

var data: Variant = JSON.parse_string(text)
if data == null or not data is Dictionary:
    push_error("...")
    return {}
return data

Priority: P1 · Size: S (was XS — expanded from 1 file to 8) · Status: Ready

[niyazmft]

Audit update 2026-06-08: Expanded scope from 1 file to 8 files. All use the legacy JSON.new().parse() pattern. Size increased from XS to S.

[google-labs-jules]

Jules is on it. When finished, you will see another comment and be able to review a PR.

[google-labs-jules]

Ready for a review! A PR has been created.