Improve Markdown rendering ergonomics for agent/bot-generated structured messages

Is your feature request related to a problem? Please describe.

I am using Nextcloud Talk as the chat surface for an agent/bot workflow (OpenClaw). The bot often sends structured operational output: short status updates, checklists, command results, links, and small reports.

In this use case the current Markdown rendering is hard to use for generated messages:

• Tables are not rendered as tables, so compact status/report data becomes difficult to scan.
• Some Markdown behavior can surprise users, e.g. numbered lines may be renumbered by Markdown rendering. This overlaps with #16034.
• Rich structured output often has to be manually simplified into plain bullets to avoid poor rendering in Talk.
• This makes Talk less ergonomic as an automation/agent notification surface compared with other chat clients.

Describe the solution you'd like

Please consider improving Talk's message rendering for bot/API-generated structured messages:

• Support GitHub-style Markdown tables in chat messages, or provide an explicit supported subset for tables/status reports.
• Preserve literal numbered lists when the sender wants plain text, or make the Markdown/plain-text behavior more predictable for API/bot senders.
• Document clearly which Markdown constructs are supported for chat messages and bot/API messages.
• Ideally allow API/bot senders to choose between text/plain and a richer Markdown mode in a way that is reflected consistently across web, desktop, and mobile clients.

Describe alternatives you've considered

The current workaround is to force all agent output into short bullet lists and avoid tables/code-heavy output. This works, but it loses useful structure and makes generated task reports harder to scan.

Additional context

Related existing issues:

• #1027 added/tracked basic text formatting.
• #16034 reports misleading Markdown behavior with numbered lines.
• #13653 reports backslash escaping/removal problems in rendered messages.

This request is specifically about improving the experience for structured, machine-generated Talk messages from bots/agents, not about replacing the existing simple chat UX.

No file, test, or entry point is named. Start by locating Talk's message Markdown rendering and API/bot message handling, then review related issues #16034 and #13653. Done would require an agreed supported behavior for tables and numbered text, consistent rendering across clients, and documentation of the supported message formats.