macbook: mbpfan back with early ramp; SMC idles fan at 79C

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

hosts/FredOS-Macbook.nix

@@ -32,9 +32,18 @@
     services.tlp.enable = false;
     services.power-profiles-daemon.enable = true;
 
-    # No mbpfan: measured 5813 of 6500 RPM at idle, so the SMC firmware is
-    # already ramping hard on its own. A more aggressive curve has nothing
-    # left to give — the cooling path itself is the limit.
+    # The SMC holds the fan at its 1200 RPM floor while the package sits at
+    # 79C — measured 1210 RPM at settled idle. (An earlier 5813 RPM reading
+    # was a rebuild spinning down, not the steady state.) Nothing in-tree
+    # ramps applesmc, so drive it directly and start well before 79C.
+    services.mbpfan = {
+      enable = true;
+      settings.general = {
+        low_temp = 55;   # below this, coast at minimum
+        high_temp = 65;  # start climbing here
+        max_temp = 80;   # full tilt — the old ceiling was above idle temp
+      };
+    };
 
     # Haswell's own thermal management: throttle gradually via RAPL/P-states
     # instead of waiting for the hardware's PROCHOT emergency brake.