fix(reader): honor line spacing over publisher styles

Ensure explicit reader spacing overrides higher-specificity EPUB typography and cover the cascade with a regression test.

Fixes #1302

client/src/features/reader/epub/composables/__tests__/useReaderState.spec.ts

@@ -142,12 +142,33 @@ describe('useReaderState', () => {
     const css = state.generateCSS()
 
     expect(css).toContain('font-family: serif !important;')
-    expect(css).toContain('line-height: 1.8;')
+    expect(css).toContain('line-height: 1.8 !important;')
     expect(css).toContain('font-size: 20px;')
     expect(css).toContain('text-align: start !important;')
     expect(css).toContain('hyphens: none;')
   })
 
+  it('overrides a more specific publisher line height on body text', () => {
+    const state = useReaderState()
+    state.setLineHeight(3)
+
+    const publisherStyle = document.createElement('style')
+    publisherStyle.textContent = '.TX { line-height: 1.31; }'
+    const readerStyle = document.createElement('style')
+    readerStyle.textContent = state.generateCSS()
+    const paragraph = document.createElement('p')
+    paragraph.className = 'TX'
+
+    document.head.append(publisherStyle, readerStyle)
+    document.body.append(paragraph)
+
+    expect(getComputedStyle(paragraph).lineHeight).toBe('3')
+
+    paragraph.remove()
+    publisherStyle.remove()
+    readerStyle.remove()
+  })
+
   it('preserves publisher paragraph margins at the default spacing', () => {
     const state = useReaderState()
 

client/src/features/reader/epub/composables/useReaderState.ts

@@ -230,7 +230,7 @@ export function useReaderState() {
           }
       }
       html {
-          line-height: ${lh};
+          line-height: ${lh} !important;
           hanging-punctuation: allow-end last;
           orphans: 2;
           widows: 2;
@@ -276,7 +276,7 @@ export function useReaderState() {
           : ''
       }
       p, li, blockquote, dd {
-          line-height: ${lh};
+          line-height: ${lh} !important;
           text-align: ${j ? 'justify' : 'start'} !important;
           hyphens: ${h ? 'auto' : 'none'};
       }