template create/make exit 0 on errors, and template list --json can emit invalid JSON #18

Found during the strictness refactor (#17); behavior unchanged there because it alters the CLI contract.

• commands/template/create.py (~75-85) and make.py (~136-141): template not found, cancelled prompt, undeterminable project dir, declined overwrite, existing template, and missing library path all exit 0. They should exit non-zero.
• kilm template list --json: an empty listing and the root update notice (main.py ~129) can print non-JSON to stdout. JSON mode should write only JSON to stdout and send notices to stderr.
• A template hook script and create both print a success message.