Enhance toolbox search: index categories, normalize queries, add category open buttons and styles

[tracygardner]

Motivation

• Improve the Blockly toolbox search to include category results and make queries more robust across localization and whitespace differences.
• Surface category results in the search flyout and allow users to jump into toolbox categories from search results.
• Provide visual affordance for category search hits by adding CSS styling for flyout buttons.

Description

• Replaced getBlocksFromToolbox with getSearchableToolboxItems that returns both toolboxBlocks and toolboxCategories, and avoids indexing search-only toolbox entries.
• Added query normalization helpers normalizeSearchSegment and normalizePathKey, and resolveToolboxName/resolveCategoryColour to handle localized names and category colours/styles consistently.
• Indexes category meta entries alongside blocks, appends category entries to the search index, and adds category buttons to the flyout via createXmlFromJson + button XML when a match is a category.
• Implemented a scoreMatch comparator to prioritize category matches, exact matches, prefixes, and then alphabetic order, and wired sorting into showMatchingBlocks.
• Registered a SEARCH_OPEN_CATEGORY button callback that finds the matching toolbox category, expands parents, selects it, and focuses the toolbox/flyout to open the category contents.
• Added CSS rules in style.css for .blocklyFlyoutButton.search-category-result to style category-result buttons with a configurable --search-category-colour variable.
• Kept the existing behavior of deferring index builds (using requestIdleCallback / setTimeout) and preserved existing search initialization patching logic.

Testing

• Ran lint and static checks via npm run lint and they completed successfully.
• Built the frontend with npm run build and the build succeeded without errors.
• Executed the test suite with npm test and all automated tests passed.

---

Codex Task