feat(snippets): add text transform for cleaning inline double dollar equations

- Implement `Clean Inline Double Dollar Symbols` text transform snippet.
- Convert inline double dollar signs `$$` to single dollar sign `$`.
- Keep block/display equation dollar signs (`$$`) intact (e.g. multi-line blocks or single-line equations starting/ending with `$$`).
- Add unit tests in `test_helpers/transforms.test.ts` to verify behavior.
- Update documentation in `docs/features/snippets.md` to document the new and existing double-dollar cleanup transforms.

docs/features/snippets.md

@@ -32,5 +32,7 @@ The **Run Text Transform Snippet** command processes your highlighted editor tex
 | **Title Kebab Case** | `Example-Text-String` | Title heading slugifications. |
 | **Title Case** | `Example Text String` | Formatting article or note headings. |
 | **Clean Zotero Highlight** | Reformats HTML tags to raw markdown | Converting Zotero desktop highlights into blockquotes. |
+| **Clean Double Dollar Symbols** | `$$` → `$` | Replaces all double dollar signs with single dollar signs in the selected text/line. |
+| **Clean Inline Double Dollar Symbols** | `$$x$$` → `$x$` | Converts inline double dollar math into single dollar inline math while preserving display/block math blocks. |
 
 When any transformation runs, TeXcore displays a notice toast in the top-right corner indicating whether the change was successfully applied.

src/features/snippets/transforms.ts

@@ -77,6 +77,22 @@ function cleanDoubleDollarSymbols(input: string): string {
   return input.replace(/\$\$/g, '$');
 }
 
+function cleanInlineDoubleDollarSymbols(input: string): string {
+  const lines = input.split(/\r?\n/);
+  const processedLines = lines.map(line => {
+    const trimmed = line.trim();
+    const isBlockEquation =
+      trimmed === '$$' ||
+      (trimmed.startsWith('$$') && trimmed.endsWith('$$') && trimmed.length > 2);
+    if (isBlockEquation) {
+      return line;
+    }
+    return line.replace(/\$\$/g, '$');
+  });
+  const hasCarriageReturn = input.includes('\r\n');
+  return processedLines.join(hasCarriageReturn ? '\r\n' : '\n');
+}
+
 export const BUILTIN_TEXT_TRANSFORM_SNIPPETS: TextTransformSnippet[] = [
   {
     id: 'kebab-case',
@@ -112,6 +128,13 @@ export const BUILTIN_TEXT_TRANSFORM_SNIPPETS: TextTransformSnippet[] = [
     description: 'Replace all $$ with $',
     keywords: ['dollar', 'latex', 'equation', 'cleanup'],
     transform: cleanDoubleDollarSymbols
+  },
+  {
+    id: 'clean-inline-double-dollar-symbols',
+    name: 'Clean Inline Double Dollar Symbols',
+    description: 'Replace inline $$ with $ while keeping block $$',
+    keywords: ['dollar', 'latex', 'equation', 'inline', 'cleanup'],
+    transform: cleanInlineDoubleDollarSymbols
   }
 ];
 

test_helpers/transforms.test.ts

@@ -0,0 +1,49 @@
+import { BUILTIN_TEXT_TRANSFORM_SNIPPETS } from '../src/features/snippets/transforms';
+
+describe('transforms.ts tests', () => {
+  const inlineDoubleDollarTransform = BUILTIN_TEXT_TRANSFORM_SNIPPETS.find(
+    s => s.id === 'clean-inline-double-dollar-symbols'
+  )?.transform;
+
+  it('should exist', () => {
+    expect(inlineDoubleDollarTransform).toBeDefined();
+  });
+
+  if (inlineDoubleDollarTransform) {
+    it('should convert inline $$ to $ while keeping block $$', () => {
+      const sample = `At low concentrations, however, the expansion,
+$$
+\\varepsilon_{\\rm reg}(k)=b_0^*+b_2^*k^2+\\cdots
+$$
+has $$b_0^*$$ dominated by water dipole correlations, so $$E^*(\\kappa)\\approx\\varepsilon_{\\rm dip}(c)$$`;
+
+      const expected = `At low concentrations, however, the expansion,
+$$
+\\varepsilon_{\\rm reg}(k)=b_0^*+b_2^*k^2+\\cdots
+$$
+has $b_0^*$ dominated by water dipole correlations, so $E^*(\\kappa)\\approx\\varepsilon_{\\rm dip}(c)$`;
+
+      expect(inlineDoubleDollarTransform(sample)).toBe(expected);
+    });
+
+    it('should keep block $$ with leading spaces', () => {
+      const sample = `  $$
+\\varepsilon = b
+  $$`;
+      expect(inlineDoubleDollarTransform(sample)).toBe(sample);
+    });
+
+    it('should keep single-line block equation', () => {
+      expect(inlineDoubleDollarTransform('$$ x = y $$')).toBe('$$ x = y $$');
+      expect(inlineDoubleDollarTransform('  $$ x = y $$  ')).toBe('  $$ x = y $$  ');
+    });
+
+    it('should handle single-line input for inline $$', () => {
+      expect(inlineDoubleDollarTransform('has $$b_0^*$$')).toBe('has $b_0^*$');
+    });
+
+    it('should handle inline equation that starts at beginning of line but has text on same line', () => {
+      expect(inlineDoubleDollarTransform('$$b_0^*$$ is the value')).toBe('$b_0^*$ is the value');
+    });
+  }
+});