fix: toolbox search final trigram

[goughjo02]

The basics

• I validated my changes

The details

Resolves

Fixes #2645

Proposed Changes

• Include the final trigram when generating search tokens to prevent partial matches on long queries.
• Add a regression test covering the “conso” false positive case.
• Expand BlockSearcher tests for short/empty input, underscore normalization, dropdown alt text indexing, and disambiguation between similar blocks.

Reason for Changes

• Prevent toolbox search from returning false positives for queries longer than three characters and improve overall search accuracy.

Test Coverage

• npm test -- --runInBand (blockly-scripts test)

Documentation

• No documentation updates needed.

Additional Information

• Additional tests define temporary blocks/dropdowns to exercise edge cases; no user-facing behavior changes beyond correcting search results.

[gonfunko]

Thank you for identifying and reporting this issue and sending a fix! I really appreciate the improved tests as well. I just had two minor questions, and if you could run npm run format and commit the results of that to make the linter happy I think we should be good to merge this.

[gonfunko]

If the test is verifying that underscores in the block type get treated as spaces, should this be 'searcher underscore block'? As written this would match the unmodified message, but not verify the normalization of the block type.

[gonfunko]

This doesn't appear to actually be a valid image; if it doesn't otherwise cause problems, can you set src to '' here and below to avoid confusion as to what this is and whether the particular value is relevant to the test case?