TP-12 — Implement filesystem theme scan

[ZhuchkaTriplesix]

Epic: B
Depends on: TP-10, TP-11

Source: docs/theme-parser-github-issues.md

Goal

Scan app support theme folder and return lightweight ThemeDefinition objects.

Files

• lib/core/theme/theme_registry_service.dart
• test/core/theme/theme_registry_service_test.dart

Implementation

Add:

class ThemeRegistryService {
  Future<List<ThemeDefinition>> loadThemeDefinitions();
}

For .json and .jsonc files:

1. Read file async.
2. Detect format:
   • if root schema == querya.theme.v1 -> custom;
   • otherwise try VS Code manifest.
3. Extract only metadata:
   • id
   • name
   • type/isDark
   • format
   • path
   • lastModified
   • contentHash
4. Skip broken files from list or return a disabled/error definition. Prefer disabled/error definition if UI should show it later.

Performance Notes

• Do not construct QueryaTheme.
• Do not construct ThemeData.
• Hash file content once during scan.
• Async file IO only.

Acceptance Criteria

• Valid custom files appear.
• Valid VS Code files appear.
• Broken file does not crash scan.
• Only .json / .jsonc are considered.

Tests

• temp dir with 2 valid themes and 1 broken;
• stable ordering by name;
• content hash changes when file changes.

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