feat(repl): usability batch - errors, WORDS, .S, BYE, DUMP, history

Core:
- Uncaught THROW prints its standard message ("Stack underflow
  (throw -4)"; unknown codes as "Catch = <n>") instead of the
  "forth-throw" sentinel. ABORT" text is carried as a structured
  payload and shown only when the -2 throw goes uncaught -- CATCH
  stays silent and the payload cannot go stale. ABORT throws -1
  through the same path.
- WORDS: optional same-line substring filter (WORDS FDEPTH), skips
  internal words (new INTERNAL header flag, set at create for
  underscore-prefixed names), wraps at 78 columns, prints a count.
  ORDER names wids (FORTH / wid#N) instead of Rust debug output.
- .S honors BASE. New: F.S (float stack), DUMP (hex+ASCII,
  bounds-checked, 4K cap), ? (fetch-and-print, boot.fth). BYE is a
  real word now: sets a VM flag the driver honors (exits REPL,
  stops rest of line/file).

CLI:
- Persistent history (~/.local/state/wafer/history, 0600 perms,
  $WAFER_HISTORY override), Tab completion over the live dictionary
  (snapshot refreshed after each line), Up/Down do prefix history
  search, Ctrl-C clears the line instead of exiting.

Web:
- History survives reloads (localStorage, cap 200, dedup, init-code
  runs excluded), User Words palette populated via new words()
  export, stack bar annotates non-decimal BASE, base() reads the
  real BASE sysvar instead of returning a hardcoded 10.

crates/web/src/lib.rs

@@ -6,8 +6,9 @@ use send_wrapper::SendWrapper;
 use wasm_bindgen::prelude::*;
 
 use wafer_core::config::WaferConfig;
-use wafer_core::memory::{CELL_SIZE, PAD_BASE, PAD_SIZE};
+use wafer_core::memory::{CELL_SIZE, PAD_BASE, PAD_SIZE, SYSVAR_BASE_VAR};
 use wafer_core::outer::ForthVM;
+use wafer_core::runtime::Runtime;
 use wafer_core::runtime::{HostAccess, HostFn};
 
 use crate::runtime_web::WebRuntime;
@@ -53,9 +54,12 @@ impl WaferRepl {
 
     /// Get the current number base (10 = decimal, 16 = hex).
     pub fn base(&mut self) -> u32 {
-        // BASE is stored at SYSVAR_BASE_VAR in WASM memory
-        self.vm.take_output(); // no-op side effect; just return base
-        10 // TODO: read from memory once we have a getter
+        self.vm.runtime_mut().mem_read_i32(SYSVAR_BASE_VAR) as u32
+    }
+
+    /// Names of all user-facing words (visible, non-internal), newest first.
+    pub fn words(&self) -> Vec<String> {
+        self.vm.word_names()
     }
 
     /// Reset the VM to initial state.