Implement complete Floating-Point word set, 70+ float words

Separate float stack with fsp global, IEEE 754 double precision.
Stack ops: FDROP FDUP FSWAP FOVER FROT FDEPTH
Arithmetic: F+ F- F* F/ FNEGATE FABS FMAX FMIN FSQRT FLOOR FROUND F**
Comparisons: F0= F0< F= F< F~
Memory: F@ F! SF@ SF! DF@ DF! FLOAT+ FLOATS FALIGNED FALIGN
Conversions: D>F F>D S>F F>S
Trig: FSIN FCOS FTAN FASIN FACOS FATAN FATAN2 FSINCOS
Exp/Log: FEXP FEXPM1 FLN FLNP1 FLOG FALOG
Hyperbolic: FSINH FCOSH FTANH FASINH FACOSH FATANH
I/O: F. FE. FS. REPRESENT >FLOAT PRECISION SET-PRECISION
Defining: FVARIABLE FCONSTANT FVALUE FLITERAL
Float literal parsing (1E, 1.5E2, -3.14E0 format)
299 unit tests + 11 compliance tests, 0 errors on float test suite

crates/core/src/dictionary.rs

@@ -111,6 +111,12 @@ impl Dictionary {
         Ok(WordId(fn_index))
     }
 
+    /// Reserve a function index without creating a dictionary entry.
+    /// Used for anonymous host functions (e.g., float literals during compilation).
+    pub fn reserve_fn_index(&mut self) {
+        self.next_fn_index += 1;
+    }
+
     /// Reveal the most recent word (remove HIDDEN flag).
     /// Called after `: ... ;` completes compilation.
     pub fn reveal(&mut self) {