config: enable API efficiency indicator in status line

Enable Phase 3 API efficiency component by default:
- Shows API time vs total session time ratio
- Helps identify sessions heavy on thinking vs generation
- Format: ⚡ 50% (green >50%, yellow <20%)

Example status line with API efficiency:
[Sonnet 4.5] | ... | ⚡ 50% | ⏱️ 2m

Users can disable by setting Config.SHOW_API_EFFICIENCY = False

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: blalterman

.claude/statusline.py

@@ -75,8 +75,8 @@ class Config:
     Set to False to disable specific indicators and reduce status line length.
     """
 
-    # Phase 3: Optional advanced components (disabled by default)
-    SHOW_API_EFFICIENCY = False  # API time vs total time ratio
+    # Phase 3: Optional advanced components
+    SHOW_API_EFFICIENCY = True  # API time vs total time ratio
     SHOW_SESSION_SOURCE = False  # How session started (resume/compact/fresh)
 
     # Core components (always enabled)