json_escape escaped only \ " \n \r \t. Every result/status string it builds
(FINAL_MSG, branch, channel, warnings) can carry text from git/ps/hermes
output; a raw ESC, BEL or any other char below 0x20 made the whole
.hermes-update-result.json invalid, and the Desktop dropped the outcome.
The remaining control chars are now written as \u00XX. Bash 3.2 compatible:
printf -v, no forks; the loop runs only when the string holds a control char.
Test (RED at start): json_escape over chars 1..127 plus UTF-8 and an ANSI
colour sequence round-trips through json.loads, in the C and C.UTF-8 locales.
review S7
684e7d713f