Fixes two bugs in the release tool.
## 1. RC tags chosen over release tags on release branches
`allSemverTags()` and `mergedSemverTags()` rely on `git tag
--sort=-v:refname` for ordering. Git's version sort treats pre-release
suffixes (e.g. `-rc.0`) as *greater* than the base release version,
which is the opposite of semver where `v2.32.0 > v2.32.0-rc.0`.
When the release branch code iterates the tag list looking for the first
matching `major.minor`, it finds the RC tag first, leading to incorrect
version suggestions (e.g. suggesting `v2.32.0` again instead of
`v2.32.1`).
**Fix:** Re-sort parsed tags using the existing `GreaterThan` method via
a new `sortVersionsDesc` helper.
## 2. Misleading mainline changelog blurb on ESR/older branch patches
When releasing a patch on an older branch (e.g. `release/2.29` for ESR),
the version is neither mainline nor stable. Declining the stable prompt
would always produce the mainline changelog note ("This is a mainline
Coder release..."), which is incorrect.
**Fix:** Only emit the mainline note when the version's minor matches
the current mainline series. For older branches the changelog omits the
note entirely.
> Generated by Coder Agents
Garrett Delfosse
a8222e02e5