helwasm: hierarchical quick-gen, pure sugar over the engine

Quick form now drives the one shared engine through commands only, so it and the
console give identical results (form == console).

- password hook answers only the "/" prompt, so read_master climbs and computes
  every ^parent from a single root master (Req 4)
- new master in the field is authoritative via `unpass`; empty field reuses the
  stored session master, so later names generate without re-typing it (Req 1/2)
- `unpass` with no name now clears ALL cached masters (real command, not a private
  hook) so the form stays reproducible in the console
- result colour = root master marked correct (correct / / uncorrect /), derived
  live from the engine; black otherwise (Req 3)
- Mark-correct toggle button; click the master to reveal it; honest memory-only hint
- master stays in memory only, never written to storage; only the one-way correct
  hash is saved on the device

parser: bare-name forms now keep a trailing comment, and a ^-led token is never a
name, so `name ^parent` / `name MODE ^parent` link the parent instead of qpname
reading it as prefix+name (was silently mis-stored).

hel/src/structs.rs

@@ -97,7 +97,7 @@ pub enum Command<'a> {
     Enc(Name),
     Gen(u32, PasswordRef),
     Pass(Name, Option<String>),
-    UnPass(Name),
+    UnPass(Option<Name>),
     Correct(Name),
     Uncorrect(Name),
     PasteBuffer(String),
@@ -153,7 +153,8 @@ impl<'a> std::fmt::Display for Command<'a> {
             Command::Gen(a, b) => write!(f, "gen{} {}", a, b.lock().borrow().to_string().trim()),
             Command::Pass(a, None) => write!(f, "pass {}", a),
             Command::Pass(a, Some(b)) => write!(f, "pass {} {}", a, b),
-            Command::UnPass(s) => write!(f, "unpass {}", s),
+            Command::UnPass(None) => write!(f, "unpass"),
+            Command::UnPass(Some(s)) => write!(f, "unpass {}", s),
             Command::Correct(s) => write!(f, "correct {}", s),
             Command::Uncorrect(s) => write!(f, "uncorrect {}", s),
             Command::PasteBuffer(s) => write!(f, "pb {}", s),