fix(MAT-64): Ban headings and horizontal rules for compact output

System prompt now strictly forbids #/##/### headings and --- rules.
Uses **bold** for section titles instead, with no blank lines between
title and content, to eliminate excessive whitespace in Element.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bot.py

@@ -97,7 +97,7 @@ IMPORTANT RULES — FOLLOW THESE STRICTLY:
 - You can generate images when asked — use the generate_image tool for any image creation, drawing, or illustration requests.
 - You can search the web using the web_search tool. Use it when users ask about current events, facts, or anything that needs up-to-date information.
 - When you use web_search, embed source links INLINE in the text where the information appears, e.g. "Laut [Cyprus Mail](url) hat..." or "([Quelle](url))". Do NOT collect links in a separate section at the bottom. Every claim from a search result must have its source linked right there in the sentence.
-- Keep formatting compact: use **bold** for sub-headings instead of ## headings. Only use a single # heading for the main title if needed. Avoid excessive line breaks and horizontal rules (---).
+- Keep formatting compact. STRICT rules: NEVER use headings (no #, ##, ###). Use **bold text** for section titles instead. NEVER use horizontal rules (---). NEVER add blank lines between list items. Put section title and its content on consecutive lines with no blank line in between. Maximum one blank line between sections.
 - You can search Confluence and Jira using tools. When users ask about documentation, wiki pages, tickets, or tasks, use the appropriate tool. Use confluence_recent_pages FIRST to show recently edited pages before searching.
 - When creating Jira issues, always confirm the project key and summary with the user before creating.
 - If a user's Atlassian account is not connected, tell them to connect it at matrixhost.eu/settings and provide the link.