perf(theme): cache tokenColorsHash on QueryaTheme to eliminate Object.hashAll in QueryaCodeEditor.build() #1353

Summary

In lib/core/editor/querya_code_editor.dart (lines 148, 296–298) and lib/core/editor/syntax_highlight_service.dart (lines 63–67):

• During every build pass of QueryaCodeEditor:
  final tokenHash = Object.hashAll(queryaTheme.tokenColors);
• In SyntaxHighlightService.createPair:
  Object.hash(language, queryaTheme.editor, Object.hashAll(queryaTheme.tokenColors))

A full VS Code theme (imported or built-in) typically contains 100–300+ TokenColorRule objects. Calling Object.hashAll on a 300-element list on every build of the code editor (which can trigger on cursor blinking, selection updates, or ancestor rebuilds) iterates through every rule to compute hash codes.

Proposed Solution

1. Compute and store final int tokenColorsHash once on QueryaTheme during construction/parsing.
2. Replace Object.hashAll(queryaTheme.tokenColors) in QueryaCodeEditor and SyntaxHighlightService with queryaTheme.tokenColorsHash.

Acceptance Criteria

• QueryaTheme caches the precomputed hash of its tokenColors.
• QueryaCodeEditor.build() performs an (1)$ integer comparison instead of iterating through all token rules.