fix(ovsm): Suppress clippy::approx_constant warnings in test fixtures

Add #[allow(clippy::approx_constant)] to test functions that use
hardcoded float values like 3.14, 3.14159, and SQRT_2 approximations.

These are test fixtures validating LISP literal parsing and math
functions, not constant definitions. The approximate values are
intentional for testing purposes.

## Changes

- lisp_comprehensive_tests.rs: Allow approx_constant in test_literals_floats and test_const_definition
- lisp_e2e_tests.rs: Allow approx_constant in test_sqrt_float and test_abs_negative_float

## Results

✅ OVSM crate: 0 warnings
✅ OVSM tests: 391 passed
✅ Formatting: 100% compliant

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

Co-Authored-By: Claude <[email protected]>

Author: 0xrinegade

crates/ovsm/tests/lisp_comprehensive_tests.rs

@@ -34,6 +34,7 @@ fn test_literals_integers() {
 }
 
 #[test]
+#[allow(clippy::approx_constant)]
 fn test_literals_floats() {
     assert_eq!(execute_lisp("3.14").unwrap(), Value::Float(3.14));
     assert_eq!(execute_lisp("-2.5").unwrap(), Value::Float(-2.5));
@@ -265,6 +266,7 @@ fn test_set_incremental_mutation() {
 }
 
 #[test]
+#[allow(clippy::approx_constant)]
 fn test_const_definition() {
     let source = r#"
         (const PI 3.14159)

crates/ovsm/tests/lisp_e2e_tests.rs

@@ -937,6 +937,7 @@ fn test_sqrt_basic() {
 }
 
 #[test]
+#[allow(clippy::approx_constant)]
 fn test_sqrt_float() {
     let source = "(sqrt 2.0)";
     let mut scanner = SExprScanner::new(source);
@@ -1029,6 +1030,7 @@ fn test_abs_negative_int() {
 }
 
 #[test]
+#[allow(clippy::approx_constant)]
 fn test_abs_negative_float() {
     let source = "(abs -3.14)";
     let mut scanner = SExprScanner::new(source);