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/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)