Dialect roadmap: v1 strings → v7 processes

[softwarewrighter]

Tracking issue for Tinytalk dialect upgrades, ordered by impact-to-
effort ratio. Each level unlocks a class of demos that read naturally
over UART. Numbering is a sketch; actual ordering may differ.

v1: strings + literal pool + Transcript

• String class, literal-pool bytecode (PUSH_LIT generalized or
  PUSH_STR), `String>>length` / `>>at:` / `>>,`,
  `SmallInteger>>printString`, `Transcript show:` / `cr`.
• Biggest user-visible upgrade. Output goes from "7" to
  "3 + 4 = 7", which makes nearly every demo readable.
• Unlocks: pretty calc, ELIZA-lite, single-room MUD, Caesar cipher,
  Roman numerals, JUnit-style test runner, friendly `guess`.

v2: blocks + BlockContext

• Block literal, BlockContext frame, `value` / `value:` /
  `value:value:` primitives.
• Biggest "feel" upgrade — control flow as message send.
• Replaces D3's eager-argument `ifTrue:ifFalse:` cheat with the
  real form. Enables `whileTrue:`, `timesRepeat:`, `do:`,
  `inject:into:`.

v3: fixed-size arrays + indexed access

• `Array` class, `at:` / `at:put:` primitives.
• Unlocks: Sieve of Eratosthenes, bubble/quicksort, Conway's Life
  on a UART-renderable grid.

v4: variable-size collections

• `OrderedCollection`, `Set`, `Dictionary` in Smalltalk on
  top of v3 arrays.
• Iterators `do:` / `collect:` / `select:` / `reject:` /
  `inject:into:` (all on top of v2 blocks).
• Unlocks: N-queens (backtracking), symbol→value lookup, real
  parser with token streams.

v5: doesNotUnderstand:

• `Object>>doesNotUnderstand:` hook in LOOKUP miss path.
• Unlocks: transparent message-logging proxy, MUD-style command
  shell where verbs are selectors, lazy method materialization.

v6: exceptions

• `[ ... ] on: Error do: [:e | ...]`, `Error signal:`,
  `ensure:` / `ifCurtailed:`.
• Unlocks: robust calc that recovers from `/0`, file/UART I/O
  wrappers with retry.

v7: green-thread scheduler

• `Process`, `Semaphore`, `[ ... ] fork`. Cooperative — fits
  COR24's tiny CPU well.
• Unlocks: producer/consumer, banker's algorithm, round-robin
  walkthrough.

Notes

`web-sw-cor24-smalltalk`
already supports stdin/stdout-driven interactive demos (D5 calc
proves this), so v1+ demos that read input ship in-browser
without UI changes.