fix(ai): render record links inside markdown headings in AI chat (#20074)

## Summary

Adds `h1`–`h6` component overrides to `LazyMarkdownRenderer` so that
`[[record:...]]` references placed inside markdown headings in the AI
chat are parsed by `processChildrenForRecordLinks` and rendered as
clickable `RecordLink` chips, matching the behavior already in place for
`p`, `li`, `td`, `th`, and `a`.

Fixes #20072

## Test plan

- [ ] In AI chat, ask a question whose answer places a record reference
inside a markdown heading (e.g. `## Found [[person:uuid:John Doe]]`) and
confirm a clickable `RecordLink` chip renders instead of the raw
`[[...]]` text.
- [ ] Verify heading styling (sizes, weights, margins) is unchanged.

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Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: nitin <ehconitin@users.noreply.github.com>

packages/twenty-server/src/engine/metadata-modules/ai/ai-chat/constants/chat-system-prompts.const.ts

@@ -59,6 +59,7 @@ Record References - IMPORTANT:
 - Tool responses include a "recordReferences" array with clickable links
 - ONLY use record references that are returned by tools - NEVER make up IDs
 - Copy the exact format from the tool response: [[record:objectName:recordId:displayName]]
+- Use record references only in paragraphs, lists, or markdown tables (\`| ... |\`); never in headings, code, links, or raw HTML
 - The recordId MUST be a real UUID (like "abc12345-1234-5678-abcd-123456789012")
 - DO NOT create record references before calling the tool
 - DO NOT use placeholder IDs like "rec-snowflake" or "rec-person-1"