Add bin/omarchy-release: the interactive release front door

A release train has three human moments, each one command: start (release
branch on basecamp/omarchy + notes staging PR + edge→rc advance for
minor/major), rc (pin both PKGBUILDs to the branch head as X.Y.ZrcN on the
pkgs rc branch, trigger the rc channel build, wait for publish, optional RC
ISO), and ship (final pins → promote rc→stable → tag → pins to master → GitHub
release from the staging PR body → final ISO → website bump, each step
skip-if-done so a crashed run resumes).

Bare omarchy-release is the shepherd: it derives the train state from observed
reality (remote branches, rc-branch pins, published channel dbs, tags — no
state files) and offers the correct next step. Versions are inferred from
branch names (v4-0-2 ⇒ 4.0.2rcN ⇒ v4.0.2). ship refuses to promote a commit
no RC was cut from. pick is a multi-select over merged quattro PRs,
cherry-picking merge commits. doctor pre-flights every credential and
connection. self-test wired into CI.

bin/omarchy-pkgs stays as the pin engine, driven with its db URL pointed at
the rc channel and pins committed to the standing rc branch (rebuilt as
master + pins per cut and force-pushed; the server rc worktree follows with
reset --hard).

.gitignore

@@ -34,3 +34,4 @@ pkgbuilds/symfony-cli/symfony*
 pkgbuilds/yay/yay/
 .srcdest/
 .repo-host
+.worktrees/