feat(core): SEE, SEE-IR, HELP introspection trio (WS-010)

Implements plans/01-see-introspection.md, all phases.

- see.rs: feature-free IR pretty-printer (format_ir/format_ir_with),
  exhaustive over IrOp -- a new variant fails the build, not the output.
- SEE-IR <name>: post-optimization IR view with resolved callee names,
  immediate/does> annotations; host-word and interpreter-token stubs.
- SEE <name>: verbatim source capture for colon words (multi-line,
  comments preserved, EVALUATE-nesting safe, error-path wiped, MARKER/
  REMEMBER/EMPTY roll word sources back too). Data definers (VARIABLE/
  CONSTANT/CREATE/BUFFER:/2*/F*/SYNONYM) record synthesized one-liners
  at definition time; VALUE/2VALUE/FVALUE/DEFER synthesize at SEE time
  so current values and IS targets show. Fallback chain ends at IR dump
  or host-word stub -- SEE never dead-ends on a defined word.
- HELP [<name>]: wordhelp.rs doc table with stack effect + one-line
  description for EVERY word in a fresh VM (300+ dictionary words plus
  all outer-interpreter tokens); a coverage test fails the build if a
  word is ever added undocumented. User words echo their leading
  ( ... -- ... ) comment. SEE/SEE-IR prepend the HELP line as a
  \ comment. Bare HELP prints usage.
- boot.fth colon definitions get real sources for free (they flow
  through evaluate); INTERPRETER_TOKENS gained the missing ?DO.

524 unit + 11 compliance + 9 comparison + 5 crypto + 1 bench green;
fmt/clippy clean; core still builds --no-default-features; web
wasm-pack build unchanged.

CLAUDE.md

@@ -79,7 +79,7 @@ Handle in `interpret_token_immediate()` or `compile_token()` as a special case.
 
 ## Testing
 
-- Run `cargo test --workspace` before committing (currently 431 unit + 1 benchmark + 11 compliance + 9 comparison)
+- Run `cargo test --workspace` before committing (currently 524 unit + 1 benchmark + 11 compliance + 9 comparison + 5 crypto)
 - Forth 2012 compliance: `cargo test -p wafer-core --test compliance`
 - Cross-engine comparison (vs gforth): `cargo test -p wafer-core --test comparison`
 - Performance benchmarks (release mode): `cargo test -p wafer-core --test comparison -- --nocapture --ignored`