Report build starts and successes, not just failures, to their own chat

Only failures were reported, so a push could reach the mirror with no way to
know short of querying the database by hand. Release runs now report:

- start: channel, arch, host, and the commit being built
- published: the packages and versions that went out, duration, channel URL
- no-changes: the run found nothing to build
- promoted: what advance moved between channels, including the rc bootstrap
  and fast-ring replication
- failed: unchanged, plus the commit context the other reports carry

Release traffic goes to OMARCHY_RELEASE_CHATBOT_URL, falling back to
BASECAMP_CHATBOT_URL, so build reports stop drowning the repository chat the
sync workflows post to. bin/setup reports which destination is configured.

The published list is captured after the build step because promote moves the
files out of build-output, and is capped at 25 entries so a full rebuild does
not produce an unreadable wall of chat.

helpers/basecamp-notifier.sh

@@ -1,13 +1,24 @@
 # Send notifications to Basecamp Campfire via chatbot
 #
-# Requires BASECAMP_CHATBOT_URL environment variable to be set.
-# This is the full chatbot lines URL from Basecamp, e.g.:
+# Two destinations, so release traffic does not drown the repository chat:
+#
+#   OMARCHY_RELEASE_CHATBOT_URL  release activity (starts, publishes, failures)
+#   BASECAMP_CHATBOT_URL         everything else, and the fallback when the
+#                                release URL is unset
+#
+# Each is the full chatbot lines URL from Basecamp, e.g.
 #   https://3.basecamp.com/<account>/integrations/<key>/buckets/<project>/chats/<chat>/lines
 #
-# If BASECAMP_CHATBOT_URL is not set, notifications are silently skipped.
+# With neither set, notifications are silently skipped.
+
+release_chatbot_url() {
+  echo "${OMARCHY_RELEASE_CHATBOT_URL:-${BASECAMP_CHATBOT_URL:-}}"
+}
 
 notify_basecamp() {
   local content="$1"
+  local BASECAMP_CHATBOT_URL
+  BASECAMP_CHATBOT_URL=$(release_chatbot_url)
 
   if [[ -z "${BASECAMP_CHATBOT_URL:-}" ]]; then
     return 0
@@ -60,3 +71,89 @@ notify_error() {
   notify_basecamp "$content"
 }
 
+
+# Human-friendly elapsed time: "8m 12s", "45s", "1h 4m".
+format_duration() {
+  local seconds="${1:-0}"
+  if ((seconds >= 3600)); then
+    printf '%dh %dm' $((seconds / 3600)) $(((seconds % 3600) / 60))
+  elif ((seconds >= 60)); then
+    printf '%dm %ds' $((seconds / 60)) $((seconds % 60))
+  else
+    printf '%ds' "$seconds"
+  fi
+}
+
+notify_start() {
+  local title="$1"
+  local details="${2:-}"
+
+  local content="🔨 <strong>${title}</strong>"
+  [[ -n "$details" ]] && content+="<br>${details}"
+  notify_basecamp "$content"
+}
+
+notify_success() {
+  local title="$1"
+  local details="${2:-}"
+
+  local content="✅ <strong>${title}</strong>"
+  [[ -n "$details" ]] && content+="<br>${details}"
+  notify_basecamp "$content"
+}
+
+notify_info() {
+  local title="$1"
+  local details="${2:-}"
+
+  local content="📦 <strong>${title}</strong>"
+  [[ -n "$details" ]] && content+="<br>${details}"
+  notify_basecamp "$content"
+}
+
+# "name-1.2.3-1-x86_64.pkg.tar.zst" -> "name 1.2.3-1". Package file names put
+# the architecture last and the pkgrel before it, so peel from the right.
+package_file_label() {
+  local file="$1" stem arch rest rel name_version version name
+  stem="${file%.pkg.tar.*}"
+  arch="${stem##*-}"
+  rest="${stem%-*}"
+  rel="${rest##*-}"
+  name_version="${rest%-*}"
+  version="${name_version##*-}"
+  name="${name_version%-*}"
+  printf '%s %s-%s' "$name" "$version" "$rel"
+}
+
+# Packages sitting in a build-output directory, newest build first. Excludes
+# signatures and the scratch database the builder keeps alongside them.
+built_package_files() {
+  local dir="$1"
+  [[ -d "$dir" ]] || return 0
+  find "$dir" -maxdepth 1 -name '*.pkg.tar.*' ! -name '*.sig' -printf '%f\n' 2>/dev/null |
+    grep -v '^omarchy-build\.' | sort
+}
+
+# An HTML list of built packages, capped so a 60-package rebuild does not
+# produce an unreadable wall of text in chat.
+format_package_list_html() {
+  local files="$1"
+  local limit="${2:-25}"
+  local count shown=0 line out=""
+
+  count=$(grep -c '' <<<"$files")
+  [[ -z "$files" ]] && count=0
+  ((count == 0)) && return 0
+
+  while IFS= read -r line; do
+    [[ -z "$line" ]] && continue
+    ((shown >= limit)) && break
+    out+="<br>• $(package_file_label "$line" | basecamp_html_escape)"
+    shown=$((shown + 1))
+  done <<<"$files"
+
+  if ((count > shown)); then
+    out+="<br>• …and $((count - shown)) more"
+  fi
+  echo "$out"
+}