fix(release): make the version stamp work on macOS and RPM - #85

The stamp shipped in #83 broke two of the seven build jobs.

macOS — `sed: 1: "Cargo.toml`. Two separate GNU-isms, only one of which was
obvious: BSD sed reads the argument after -i as a backup suffix, and the
`0,/re/` address range used to match only the first occurrence is a GNU
extension BSD rejects outright. Fixing the first alone would still have failed.
Uses awk instead, which behaves the same on both.

RPM — `invalid version "0.1.0-rc.10": contains invalid character (allowed:
alphanumeric, '.', '_', '+', '%', '{', '}', '~', '^')`. RPM forbids '-' in a
version, but cargo requires semver. The tool's own error names the way out: '+'
is legal in RPM, and semver allows it as build metadata. So the pre-release
marker becomes +rc.N rather than -rc.N, which cargo, dpkg and rpm all accept.
'~' would sort better for rpm and deb, but cargo rejects it.

This is the same failure I made earlier today with BSD grep in
non_utf8_argv_test: verified against GNU tooling on Windows, shipped to a macOS
runner. Checked explicitly for it this time — the awk rewrite was prompted by
noticing the 0,/re/ range would fail on BSD even after the -i fix.

Verified:
- all five tag forms derive correctly
- cargo metadata reports 0.1.0+rc.10
- 0.1.0+rc.10 contains only characters rpm's error message lists as legal
- the stamp rewrites line 3 only; clap/serde/serde_json versions intact
- the stable path yields a bare 0.1.0
- a malformed tag is rejected rather than corrupting the manifest

Still unverified locally: the .deb/.rpm filenames, which need cargo-deb and
cargo-generate-rpm on Linux, and BSD sed/awk behaviour itself. The next RC's
published assets and the macOS job are the checks.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>