Stop the rc unit failing before the first RC is cut

The rc service fetched and reset /root/omarchy-pkgs-rc in ExecStartPre, but
that worktree does not exist until the first RC creates the rc branch — so on
a freshly set up host the unit failed every five minutes, forever, and showed
up as a failed unit in the timer report.

It now runs bin/auto-release-rc from the main checkout, which always exists:
nothing queued exits silently, no rc branch is a clean no-op, and a missing
worktree is created on demand before handing off to the worktree's own
auto-release.

bin/auto-release-rc

@@ -0,0 +1,43 @@
+#!/bin/bash
+# Scheduled entry point for the rc channel.
+#
+# The rc channel builds from the standing `rc` branch in its own worktree, but
+# that branch does not exist until the first RC is cut — and a host set up
+# before then has no worktree either. This runs from the MAIN checkout, which
+# always exists, and makes both conditions non-events: no branch means nothing
+# to build, and a missing worktree is created on demand rather than failing
+# the unit every five minutes.
+
+set -e
+
+BUILD_ROOT=$(realpath "${BASH_SOURCE[0]%/*}/..")
+source "$BUILD_ROOT/helpers/message-helpers.sh"
+
+RC_WORKTREE="${OMARCHY_RC_WORKTREE:-/root/omarchy-pkgs-rc}"
+STATE_DIR="${OMARCHY_STATE_DIR:-/root/.state}"
+
+# Nothing queued: the common case. Exit before touching the network.
+[[ -f "$STATE_DIR/.sync-needed-rc" ]] || exit 0
+
+git -C "$BUILD_ROOT" fetch --quiet origin rc 2>/dev/null || true
+
+if ! git -C "$BUILD_ROOT" show-ref --verify --quiet refs/remotes/origin/rc; then
+  print_info "No rc branch yet — nothing to build (the first RC cut creates it)"
+  exit 0
+fi
+
+if [[ ! -d "$RC_WORKTREE" ]]; then
+  print_info "Creating rc worktree at $RC_WORKTREE..."
+  if git -C "$BUILD_ROOT" show-ref --verify --quiet refs/heads/rc; then
+    git -C "$BUILD_ROOT" worktree add "$RC_WORKTREE" rc
+  else
+    git -C "$BUILD_ROOT" worktree add --track -b rc "$RC_WORKTREE" origin/rc
+  fi
+fi
+
+# The rc branch is rebuilt as master + pins for each cut and force-pushed, so
+# this follows with a hard reset rather than a fast-forward pull.
+git -C "$RC_WORKTREE" fetch origin rc
+git -C "$RC_WORKTREE" reset --hard origin/rc
+
+exec "$RC_WORKTREE/bin/auto-release" rc