Implement Double-Number and String word sets, fix memory panics

Double-Number (19 words): D+ D- DNEGATE DABS D2* D2/ D0= D0< D= D< DU<
  DMAX DMIN D>S M+ M*/ D. D.R 2ROT 2CONSTANT 2VARIABLE 2VALUE 2LITERAL
  Double-number literal parsing (tokens ending with '.')
String (5 words): COMPARE SEARCH /STRING BLANK -TRAILING SLITERAL
Fix all memory access panics with bounds checking throughout host functions.

8 word sets at 100%: Core, Core Ext, Exception, Double, String,
  Search-Order, Memory-Allocation, Programming-Tools

crates/core/src/codegen.rs

@@ -41,14 +41,14 @@ const TYPE_I32: u32 = 1; // (i32) -> ()
 const EMIT_FUNC: u32 = 0;
 const WORD_FUNC: u32 = 1;
 
-/// Natural-alignment MemArg for 4-byte i32 operations.
+/// Natural-alignment `MemArg` for 4-byte i32 operations.
 const MEM4: MemArg = MemArg {
     offset: 0,
     align: 2, // 2^2 = 4
     memory_index: MEMORY_INDEX,
 };
 
-/// MemArg for single-byte operations.
+/// `MemArg` for single-byte operations.
 const MEM1: MemArg = MemArg {
     offset: 0,
     align: 0, // 2^0 = 1
@@ -81,7 +81,7 @@ pub struct CompiledModule {
 // Instruction-level helpers (free functions that take &mut Function)
 // ---------------------------------------------------------------------------
 
-/// Decrement `$dsp` by CELL_SIZE.
+/// Decrement `$dsp` by `CELL_SIZE`.
 fn dsp_dec(f: &mut Function) {
     f.instruction(&Instruction::GlobalGet(DSP))
         .instruction(&Instruction::I32Const(CELL_SIZE as i32))
@@ -89,7 +89,7 @@ fn dsp_dec(f: &mut Function) {
         .instruction(&Instruction::GlobalSet(DSP));
 }
 
-/// Increment `$dsp` by CELL_SIZE.
+/// Increment `$dsp` by `CELL_SIZE`.
 fn dsp_inc(f: &mut Function) {
     f.instruction(&Instruction::GlobalGet(DSP))
         .instruction(&Instruction::I32Const(CELL_SIZE as i32))

crates/core/src/dictionary.rs

@@ -5,7 +5,7 @@
 //! - Flags + name length (1 byte)
 //! - Name string (N bytes, padded to cell alignment)
 //! - Code field: function table index (4 bytes)
-//! - Parameter field: data for CREATEd words, DOES> action, etc.
+//! - Parameter field: data for `CREATEd` words, DOES> action, etc.
 
 use crate::error::{WaferError, WaferResult};
 use crate::memory::{DICTIONARY_BASE, INITIAL_PAGES, PAGE_SIZE};
@@ -57,7 +57,7 @@ impl Dictionary {
     }
 
     /// Create a new dictionary entry (like Forth's CREATE).
-    /// Returns the WordId (function table index) assigned to this word.
+    /// Returns the `WordId` (function table index) assigned to this word.
     /// The word starts HIDDEN (will be revealed when compilation completes).
     pub fn create(&mut self, name: &str, immediate: bool) -> WaferResult<WordId> {
         let name_upper = name.to_ascii_uppercase();
@@ -139,7 +139,7 @@ impl Dictionary {
         }
     }
 
-    /// Look up a word by name. Returns (word_address, word_id, is_immediate).
+    /// Look up a word by name. Returns (`word_address`, `word_id`, `is_immediate`).
     /// Searches from LATEST backward through the linked list.
     /// Skips HIDDEN words.
     pub fn find(&self, name: &str) -> Option<(u32, WordId, bool)> {
@@ -347,7 +347,7 @@ impl Dictionary {
     }
 
     /// Write a u32 in little-endian without bounds checking.
-    /// Caller must ensure addr + 4 <= memory.len().
+    /// Caller must ensure addr + 4 <= `memory.len()`.
     fn write_u32_unchecked(&mut self, addr: u32, value: u32) {
         let a = addr as usize;
         let bytes = value.to_le_bytes();
@@ -355,7 +355,7 @@ impl Dictionary {
     }
 
     /// Read a u32 in little-endian without bounds checking.
-    /// Caller must ensure addr + 4 <= memory.len().
+    /// Caller must ensure addr + 4 <= `memory.len()`.
     fn read_u32_unchecked(&self, addr: u32) -> u32 {
         let a = addr as usize;
         u32::from_le_bytes([

crates/core/src/ir.rs

@@ -93,7 +93,7 @@ pub enum IrOp {
         test: Vec<IrOp>,
         body: Vec<IrOp>,
     },
-    /// BEGIN test1 WHILE test2 WHILE body REPEAT after_repeat ELSE else_body THEN
+    /// BEGIN test1 WHILE test2 WHILE body REPEAT `after_repeat` ELSE `else_body` THEN
     ///
     /// Two nested WHILEs in a single BEGIN loop. When the first WHILE fails,
     /// control goes to `else_body`. When the second WHILE fails, control goes