Implement loop (infinite) and do...while/until loops

Completes the 'loop, next, break, do' TODO entry — break and next
were landed in the previous commit; this adds the remaining two forms:

- loop { body } — infinite loop; the only exit is break. Simpler than
  while/until since there is no condition expression to evaluate.

- do { body } while expr; / do { body } until expr; — post-condition
  loop: body always executes at least once, condition is checked at the
  bottom of each iteration. Condition tokens are collected until ';'
  (mirrors _expression_get but stops at semicolon instead of '{'), then
  replayed each iteration using the same temp-stack/temp-iterator
  technique as while/until. Both break and next are supported.

Token changes: TT_LOOP and TT_DO added to the keyword enum in token.h,
registered in get_tt() and tt_get_name() in token.c.

Add examples/loop_do.fy; expected output: 5 / 12 / 11 / 5.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/docs/version.txt b/docs/version.txt
index ea87c13..c825cd1 100644
--- a/docs/version.txt
+++ b/docs/version.txt
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-Fype Superalpha Build 9671
+Fype Superalpha Build 9673