Audit the 2024 "done" batch for mis-ticked issues #125

Two issues closed in the Feb–May 2024 push have been found materially undone:

• next: iterate, repeat, replicate, and cycle methods should just be generators #75 — claimed replicate was converted to a generator. It was not;
  packages/fjl/src/list/replicate.ts is still eager (Array(n).fill(x, 0, n)
  returning T[]). Tracked in v2.0 - feature: Update iterator family of methods to just be generators, where it makes sense #121.
• fjl v3.0: Move tests near the member call sites #77 — claimed test co-location. It did not happen; 125 of 126 test files
  are still under packages/fjl/tests/, and three naming conventions are live
  at once (test-*.ts, index_test.ts, *.test.ts).

Two independent mis-ticks in the same batch is a pattern rather than an
accident, so the remaining closures from that period should be spot checked
before #57 is declared complete.

Acceptance criteria

• Re-verify each issue closed between 2024-02-09 and 2024-06-01 against the
  current tree
• Reopen, or file follow-ups for, any whose acceptance criteria are unmet
• Correct fjl v2.0 #57's "Done" list if any of its ticked references turn out to be
  premature

This is deliberately scoped as a one-off audit, not a process change.