Improve test coverage

Added comprehensive test coverage across the module and its term_glossary_per_node submodule — 14 files changed, 2055 insertions, 5 deletions.

New test files (11)

Kernel tests

• TermGlossaryManagerTest — 18 tests for the core service: empty input, invalid UTF-8, basic/multiple term matching, case-sensitive/insensitive, full-word matching with boundary exceptions, single match per field/content, exclude self-reference, ignore tags, link/glossary-exclude class exclusion, handler resolution, config retrieval, term caching.
• TermGlossaryControllerTest — 6 tests for the JSON API endpoints: letter search (valid/invalid), term-by-ID (found/not found), search-per-term (CONTAINS match/no results).
• GlossaryAlphabeticalBockTest — 7 tests for the block plugin: default configuration, build output for all three search_type variants, form structure, form default value reflection, submit handler.
• TermGlossaryPerNodeManagerTest — 5 tests for the per-node service decorator: service override verification, vocabulary resolution with per-node override, formatter third-party settings (active/inactive/non-node entity).

Unit tests

• TermGlossaryLinkHandlerTest — 1 test for the link handler plugin: term wrapping with link URL, CSS class, and tid in URL options.
• TermGlossaryCustomJSHandlerTest — 2 tests for the custom JS handler plugin: term wrapping with data attributes and CSS classes, and HTML escaping of term names.
• TermGlossaryPerNodeHooksTest — 2 tests for per-node hook callbacks: entityBaseFieldInfo() returns fields for node type and empty array for non-node types.
• TermGlossaryUtilsTest — 6 tests for the utility class: per-node settings retrieval (active/inactive/missing type), vocabulary resolution with/without override.

Functional tests

• TermGlossaryRenderTest — 2 tests for end-to-end rendering: glos-term markup appears when glossary is enabled on a field, absent when disabled.
• TermGlossaryConfigFormTest — 2 tests for the admin config form: successful submission and access denied for anonymous users.

Shared trait

• GlossaryTestTrait — extracts duplicated setUp boilerplate (installGlossaryTestDependencies()) and the createGlossaryTerm() helper into a reusable trait shared by all 4 kernel tests and the functional render test.

Modified files (3)

• TermGlossaryPerNodeTest — added detailed PHPDoc descriptions to testNodeFormSettings() and testDisablingOverride().
• TermGlossaryHooksTest — added detailed PHPDoc descriptions to all test methods, renamed $result variables to $form_elements for clarity.
• .cspell-project-words.txt — added zzzznotfound (used in controller test).