State-smart anonymous xt builder. Interpret mode leaves the xt on the
data stack; compile mode emits a literal push into the enclosing word,
so `: APPLY EXECUTE ; [: 1 2 + ;] APPLY` prints 3.
Supported nested inside colon definitions via a new compile-frame stack
(`Vec<CompileFrame>`). Each frame snapshots `compiling_name`,
`compiling_word_id`, `compiling_word_addr`, `compiling_ir`,
`control_stack`, `saw_create_in_def`, `compiling_locals`, and `state`.
The inner [: ... ;] compiles its body as an anonymous word; on ;] the
outer frame pops back and the xt is either pushed to the data stack
(interpret mode) or compiled as a literal (compile mode).
Also fixes a latent bug: `finish_colon_def` used to reveal `latest`,
which breaks when intermediate dict entries (now including quotations)
move `latest`. Each definition now tracks its own `compiling_word_addr`
and uses `reveal_at`, matching the existing DOES> pattern.
Five tests cover interpret, compile, inside-a-colon-def, two-level
nesting, and the control-stack-travels-with-frame regression (outer
IF/ELSE/THEN must still match around an inner [: ;]).
ok2
6771f5d46b