Improve AI chat UX (#17974)

## Summary
- update AI chat message typography and list line-height for readability
- apply richer markdown-section styling for headings, spacing,
separators, and inline code
- keep links non-underlined by default with underline on hover, using
accent11 for link color
- preserve previous AI chat table design while keeping other markdown
improvements

## Validation
- yarn eslint
packages/twenty-front/src/modules/ai/components/LazyMarkdownRenderer.tsx
packages/twenty-front/src/modules/ai/components/AIChatMessage.tsx

---------

Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

packages/twenty-ui/src/json-visualizer/components/internal/JsonNodeLabel.tsx

@@ -6,7 +6,6 @@ import { type JsonNodeHighlighting } from '@ui/json-visualizer/types/JsonNodeHig
 const StyledLabelContainer = styled.span<{
   highlighting?: JsonNodeHighlighting;
 }>`
-  align-items: center;
   background-color: ${({ theme, highlighting }) =>
     highlighting === 'blue'
       ? theme.color.blue3
@@ -28,15 +27,20 @@ const StyledLabelContainer = styled.span<{
   border-radius: ${({ theme }) => theme.border.radius.sm};
   border-style: solid;
   border-width: 1px;
+  column-gap: ${({ theme }) => theme.spacing(2)};
+  display: inline-flex;
+  align-items: center;
   height: 24px;
   box-sizing: border-box;
-  column-gap: ${({ theme }) => theme.spacing(2)};
-  display: grid;
-  grid-template-columns: auto 1fr;
-  align-items: center;
+  font-size: ${({ theme }) => theme.font.size.md};
   white-space: nowrap;
-  padding-block: ${({ theme }) => theme.spacing(1)};
   padding-inline: ${({ theme }) => theme.spacing(2)};
+
+  > span {
+    align-items: center;
+    display: inline-flex;
+    line-height: 1;
+  }
 `;
 
 export const JsonNodeLabel = ({

packages/twenty-ui/src/json-visualizer/components/internal/JsonNodeValue.tsx

@@ -15,6 +15,7 @@ const StyledText = styled.span<{
         : theme.font.color.tertiary};
   display: inline-flex;
   height: 24px;
+  line-height: 1;
 `;
 
 export const JsonNodeValue = ({