fix: recognize extended chair-position placeholders as empty

The legal-analyst agent was generating a longer placeholder form
[ימולא ע"י יו"ר הוועדה — עמדה/הנחיה לגבי סוגיה זו שתשמש את סוכן הכתיבה]
which _is_placeholder() did not match (substring check fails because ] is
further along in the longer form). Result: UI showed "✓ עמדה נקבעה" (green)
for all 4 issues even though no chair direction had been entered.

Fixes:
1. research_md.py: add regex fallback — any text starting with [ימולא is a placeholder
2. legal-analyst.md: template now emits the standard short placeholder only

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

mcp-server/src/legal_mcp/services/research_md.py

@@ -55,6 +55,9 @@ def _is_placeholder(text: str) -> bool:
     for ph in CHAIR_POSITION_PLACEHOLDERS:
         if ph in stripped:
             return True
+    # Extended placeholders: [ימולא ע"י יו"ר הוועדה — extra descriptive text]
+    if re.match(r'^\[ימולא\b', stripped):
+        return True
     return False