fix(z3): robust = conversion + SQLite pager spec (DB.2)

- Fixed infix = conversion regex: global replace replaces restrictive lookbehind version
- Also catches = inside =>, and, or bodies (not just depth 0)
- Fixed implies keyword support in expression translation
- Fixed SQLitePager.speck: implies→->, string-typed enum comparison fix
- All specs (ToggleSwitch, KafkaKRaft, SQLitePager) produce zero-error SMT-LIB2
- All 37 tests pass

out/KafkaKRaft.smt2

@@ -1,6 +1,6 @@
 ; SpeckDL: KafkaKRaft — Z3 Verification
 ; Generated by speckl-compile Z3 backend
-; Bounded model checking depth: 5
+; Bounded model checking depth: 10
 
 (set-logic ALL)
 (set-option :produce-models true)
@@ -31,7 +31,7 @@
 ; --- Invariants ---
 (define-fun ElectionSafety () Bool
   (and
-    (=> (= Leader $3) (> currentTerm 0))
+    (=> (= state Leader) (> currentTerm 0))
   )
 )
 (define-fun LeaderCompleteness () Bool

out/ToggleSwitch.smt2

@@ -4,6 +4,7 @@
 
 (set-logic ALL)
 (set-option :produce-models true)
+(declare-fun speckl_len_Int ( (Array Int Int) ) Int)
 
 ; --- State Variables ---
 (declare-const isOn Bool)