Change percentage threshold from 50% to 40% for tighter outlier filtering

Rationale: 50% threshold too permissive for Israeli real estate market.
Within same room count/area, legitimate price variance typically ±30-35%, not 50%.

Example: 13,402 NIS/sqm deal (47% below 25,120 median) was passing with 50% threshold.
This is almost certainly data error or partial deal, not legitimate market variation.

Changes:
- ANALYSIS_PERCENTAGE_THRESHOLD default: 0.5 → 0.4 (40%)
- Update CLAUDE.md docs to reflect 40% threshold

Impact:
- New lower bound: median × 0.6 (was median × 0.5)
- New upper bound: median × 1.4 (was median × 1.5)
- Tighter filtering while preserving legitimate high/low-end deals
- Better aligned with actual Israeli real estate market variance

Tests: All 326 tests pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

nadlan_mcp/config.py

@@ -73,7 +73,7 @@ class GovmapConfig:
         == "true"
     )
     analysis_percentage_threshold: float = field(
-        default_factory=lambda: float(os.getenv("ANALYSIS_PERCENTAGE_THRESHOLD", "0.5"))
+        default_factory=lambda: float(os.getenv("ANALYSIS_PERCENTAGE_THRESHOLD", "0.4"))
     )
 
     # Hard Bounds for Price per Sqm (catches obvious data errors)