fix(extraction): count all file-level-tracked langs (incl .properties) as indexed (#544)

Completes #357. The no-symbol file-level class is yaml/twig/properties, but the
count fix only covered yaml/twig — so a .properties-only project still printed
"No files found to index" even though the files were stored. Introduce a single
isFileLevelOnlyLanguage predicate (the canonical set behind the tree-sitter
no-symbol branch, xml excluded since its MyBatis extractor emits a file node)
and use it at both count sites and the extraction dispatch so the list can't
drift. Adds .properties regression coverage for indexAll() and indexFiles().

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/extraction/tree-sitter.ts

@@ -15,7 +15,7 @@ import {
   ExtractionError,
   UnresolvedReference,
 } from '../types';
-import { getParser, detectLanguage, isLanguageSupported } from './grammars';
+import { getParser, detectLanguage, isLanguageSupported, isFileLevelOnlyLanguage } from './grammars';
 import { generateNodeId, getNodeText, getChildByField, getPrecedingDocstring } from './tree-sitter-helpers';
 import type { LanguageExtractor, ExtractorContext } from './tree-sitter-types';
 import { EXTRACTORS } from './languages';
@@ -3072,7 +3072,7 @@ export function extractFromSource(
     // file node so the watcher tracks it without emitting symbols.
     const extractor = new MyBatisExtractor(filePath, source);
     result = extractor.extract();
-  } else if (detectedLanguage === 'yaml' || detectedLanguage === 'twig' || detectedLanguage === 'properties') {
+  } else if (isFileLevelOnlyLanguage(detectedLanguage)) {
     // No symbol extraction at this stage — files are tracked at the file-record
     // level only. Framework extractors (Drupal routing yml, Spring `@Value`
     // resolution against application.yml/application.properties) run later and