add missing tactic descriptions, add rewrite for tamagochi

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/tactic/aig/aig_tactic.h

@@ -13,7 +13,31 @@ Author:
 
     Leonardo (leonardo) 2011-10-24
 
-Notes:
+Tactic Documentation:
+
+## Tactic aig
+
+### Short Description
+
+Simplify Boolean structure using AIGs (And-inverter graphs).
+
+### Long Description
+
+And-inverter graphs (AIGs) uses just the Boolean connectives `and` and `not` to encode Boolean
+formulas. The circuit representation using AIGs first converts formulas using other connectives to this normal form, 
+then performs local simplification steps to minimize the circuit representation.
+Note that the simplification steps used by this tactic are heuristic, trading speed for power, 
+and do not represent a high-quality circuit minimization approach.
+
+### Example
+
+```z3
+(declare-const a Bool)
+(declare-const b Bool)
+(declare-const c Bool)
+(assert (or (and a b) (and b a c)))
+(apply aig)
+```
 
 --*/
 #pragma once