docs(release): justify the interpreter check from the repo, not an OS

The comment rested on `python3` being 3.9 on macOS, which is where the failure
showed up rather than why the code was wrong -- and a reader on another
platform would take it as not applying to them.

The repo-intrinsic version: this package declares requires-python >=3.10 and
tomllib is stdlib only from 3.11, so the release script could not run on the
oldest Python the package itself claims to support, on any OS. Also records why
it stayed hidden -- CI installs 3.12 through uv, so only a human cutting a
release ever ran into it.

Comment only; no behaviour change.

Author: anoop-narang

scripts/release.sh

@@ -7,11 +7,14 @@ cd "$ROOT"
 die() { echo "error: $*" >&2; exit 1; }
 need() { command -v "$1" >/dev/null 2>&1 || die "$1 is required"; }
 
-# An interpreter that can `import tomllib` — stdlib only from 3.11, while
-# `python3` on macOS is still 3.9. Hardcoding `python3` made every step below
-# fail with a bare ModuleNotFoundError, which reads as a broken checkout rather
-# than a too-old interpreter, and it failed at the FIRST step so nothing was
-# half-done. Resolved once here rather than per call site.
+# An interpreter that can `import tomllib`, which is stdlib only from 3.11.
+#
+# `python3` carries no version guarantee, and this package's own requires-python
+# is >=3.10 — so hardcoding it meant the release script could not run on the
+# oldest Python the package claims to support. CI never sees this, because it
+# installs 3.12 through uv; only a human cutting a release does, which is why it
+# went unnoticed. The symptom was a bare ModuleNotFoundError, which reads as a
+# broken checkout rather than a too-old interpreter.
 #
 # `uv` is the fallback because this repo already builds and tests through it, so
 # a machine that can run the suite can run the release.