feat: render markdown in message views

[utpalsinghdev]

Summary

Session messages and live chat currently show Markdown as raw syntax. Agent replies with headings, lists, code, and tables are hard to read.

This PR runs that content through the existing MarkdownRenderer (react-markdown + remark-gfm) after demo-mode masking. Raw HTML stays inert. javascript: URLs are not executable links. Peer representations already use this renderer.

Type

• New feature

Test plan

• pnpm lint passes
• pnpm test passes
• @openconcho/web build succeeds
• Tested in browser:
  • A session message rendered a heading, list, fenced code, GFM table, and https://example.com link
  • A <script> payload stayed visible as text and did not run
  • Demo mode masked the message heading
  • A chat reply rendered the same heading

Related issues

Closes #88

[offendingcommit]

Thanks, rendering Markdown in messages is a good change. The problem is the renderer: MarkdownRenderer is built for peer representations, and it rewrites ordinary message text in ways that break it:

• preprocessContent strips three leading spaces from every line, which mangles indented code and nested lists.
• Paragraph re-sorts and restyles paragraphs made of [YYYY-MM-DD HH:MM:SS] lines, so pasted logs come out in a different order.
• CITATION_RE turns any [10+ char token] into a session-link chip.
• A ## Inductive Observations or ## Contradictions heading sends the text through the representation-only card parsers.
• Dropping whitespace-pre-wrap collapses single newlines, so every multi-line plain-text message becomes one line.
• Contrast: user bubbles in ChatPage are var(--accent) with color: #fff, but Paragraph, ul and ol hardcode color: var(--text-2). User text loses its white color on the accent background.

Suggested fix: add a small message renderer, e.g. MessageMarkdown, using plain react-markdown + remark-gfm + remark-breaks (or pre-wrap paragraphs). Have it inherit color from the bubble, and keep the same safe-link and no-raw-HTML settings. A test with a multi-line plain message and a [2026-01-01 00:00:00] line would pin both regressions.