install.sh invoked apply_noninteractive_defaults at the top of
the file (line 96) but defined the function further down (line
102 in the prior version). With set -e, the call died with
"command not found" exit 127 before any real work happened —
which is why this environment always installed Lain manually
instead of running the official curl-pipe installer.

Fix: move the apply_noninteractive_defaults definition above
its call site. parse_args was already defined before its call,
so only the second helper needed reordering.

Bumps Cargo.toml to 0.7.2 so the binary version string and the
tag are consistent. Updates AGENTS.md to record the v0.7.2
installer fix alongside the v0.7.0 → v0.7.1 version-string
fix.

Verified by:
- bash install.sh --yes --agent claude </dev/null  → exit 0,
  installed v0.7.1 from upstream cleanly
- bash install.sh --help                             → exit 0
- bash <(git show HEAD:install.sh) --yes --agent claude
  </dev/null                                         → exit 127
  with "apply_noninteractive_defaults: command not
  found" (the original bug)