v2.22.0

A minor release: a tool result the model reads changes (edit_file when
new_string carries a literal \n and the file would not parse).

Gate: PASS on the pinned 24-case set after one recheck: agentic-1
had all five runs invalid ("backend unreachable", the server stalled when
free memory hit 1.4 GB), and re-run on a fresh server it was 6/6. Own arm,
seed 20261011, against 2.21.0's arm: run-level 184/234 vs 186/233,
−1.2 %, Fisher p = 0.82; pass^k 34 → 32 of 49, McNemar p = 0.73; 11
invalid runs of 245. The decode never fired in the arm: none of its 48
edit_file calls had a literal \n in new_string, so every edit result
was byte-identical to 2.21.0 and the arm-level movement is run-to-run
noise. The gate shows nothing broke; the benefit is not yet measured live.

• When an edit to a .py or .json file would leave it unparseable and
  new_string has a literal \n but no real line break, edit_file tries
  the decoded new_string (the full decode, then for Python one that keeps a
  quote-adjacent escape) and keeps it only if the file then parses. 139 of
  1,746 recorded edit_file calls put a literal \n in new_string, 135
  with no real line break, mostly in self-correct-1, agentic-3 and
  regression-anchor-1, and the 2.21.0 arm lost a run of each of the latter
  two to it. An escape that parses as written is never touched, and other
  file types are left alone.