Demo backlog: more v0 demos (no dialect upgrade required)

[softwarewrighter]

Tracking issue for additional demos that fit the current Tinytalk v0
dialect (24-bit tagged SmallInteger refs, 14 bytecodes, hand-assembled
drivers via POKE / DATA-loader image init). All work without new
bytecodes, strings, blocks, or collections — result is one integer in
stdout, matching D1..D7.

Backlog

• fibonacci — SmallInteger>>fib. Two recursive calls per
  frame; validates frame stack on a different recursion shape than
  D6 fact. 7 fib → 13.
• gcd — Integer>>gcd: Euclidean. Two-arg recursion.
  12 gcd: 18 → 6.
• power — Integer>>raisedTo:, tail-recursive accumulator
  with early exit at e=0. 2 raisedTo: 7 → 128.
• prime — SmallInteger>>isPrime, trial division. Returns
  1 or 0 (or reuse the D3 True/False objects).
• ackermann — A(m,n). Frame-stack stress test.
  ackermann: 2 with: 3 → 9.
• hanoi — Move count to solve N disks (no strings, so just
  print the count: `5 hanoi → 31`).
• linked-list — `Cell` class (head, tail), `Cell>>sum`
  walks the chain. First demo with a heap of cooperating user
  objects beyond Counter.
• stack / queue — push/pop/peek on a Cell chain. Identity
  • mutable state.
• state-machine — `TrafficLight` cycling 0→1→2→0 via a
  polymorphic `next` method.
• compare-mixin — `Comparable` superclass: subclasses
  override `<`, inherit `<=` / `>` / `between:and:` from
  super. Exercises the D7 inheritance walk across multiple
  selectors.

Driver-authoring cost

Each demo costs ~30-60 lines of fragile hand-assembly in BASIC
(POKE bytecodes + class-table init + DATA loaders). Worth weighing
against deferring some of these until a v1+ Smalltalk-source
compiler exists (see the dialect roadmap issue) so future demos
become `.st` files instead of bootloaders.

Web demo coverage

`web-sw-cor24-smalltalk`'s
`build.rs` auto-picks up `examples/dN_*.bas` + `src/image_dN.bas`,
so each demo lands in CLI and browser together.