feat(sync): best-effort coord visibility signal (git_sync_<machine> component)

sync.sh now posts a per-machine coord component
(claudetools/git_sync_<MACHINE>) flipped syncing -> idle/degraded around
each run, so the fleet can see who is mid-sync / last sync state. Fully
best-effort: a 3s-capped curl guarded with || true + return 0, emitted
only after the lock is acquired (contention/exit-75 emits nothing), and
finalize captures $? first and returns it so the signal can never change
the sync's real exit code. Reviewed (verified it cannot break sync).

.claude/scripts/sync.sh

@@ -91,6 +91,22 @@ else
 fi
 TIMESTAMP=$(date "+%Y-%m-%d %H:%M:%S")
 
+# --- Coord visibility signal (BEST-EFFORT, never blocks/fails the sync) -------
+# Publishes a per-machine coord component so the fleet can see this machine's
+# sync state. Pure visibility: every call is guarded so it can NEVER trip the
+# script's `set -e`, slow the sync beyond a tiny timeout, or change the exit code.
+COORD_BASE="http://172.16.3.30:8001/api/coord"
+COORD_SYNC_STARTED=0
+coord_signal() {
+    local state="${1:-}"
+    curl -s --connect-timeout 2 -m 3 -o /dev/null -X PUT \
+        "$COORD_BASE/components/claudetools/git_sync_${MACHINE}" \
+        -H "Content-Type: application/json" \
+        -d "{\"state\":\"${state}\",\"version\":\"1.0.0\",\"notes\":\"${state} at ${TIMESTAMP} (${USER_DISPLAY:-?})\",\"updated_by\":\"${MACHINE}/sync\"}" \
+        2>/dev/null || true
+    return 0
+}
+
 echo -e "${GREEN}[OK]${NC} Starting ClaudeTools sync from $MACHINE at $TIMESTAMP"
 
 # Navigate to ClaudeTools directory
@@ -141,9 +157,23 @@ SYNC_LOCK_DIR="$REPO_ROOT/.git/claudetools-sync.lock"
 # shellcheck source=./sync-lock.sh
 source "$REPO_ROOT/.claude/scripts/sync-lock.sh"
 
-trap release_sync_lock EXIT INT TERM
+# Finalize: best-effort coord signal (only if we actually started a sync), then
+# ALWAYS release the lock (idempotent + ownership-gated). $? is captured FIRST so
+# the coord branch reflects the real script outcome. This trap must NOT call
+# `exit` — letting it return preserves the script's true exit code.
+sync_finalize() {
+    local rc=$?
+    if [ "$COORD_SYNC_STARTED" = "1" ]; then
+        if [ "$rc" = "0" ]; then coord_signal idle; else coord_signal degraded; fi
+    fi
+    release_sync_lock
+    return "$rc"   # preserve the script's true exit code regardless of release_sync_lock's status
+}
+trap sync_finalize EXIT INT TERM
 acquire_sync_lock
 echo -e "${GREEN}[OK]${NC} Acquired sync lock ($SYNC_LOCK_DIR)"
+COORD_SYNC_STARTED=1   # set BEFORE the signal so a crash in the gap still finalizes (degraded)
+coord_signal syncing
 # --- end concurrency lock ----------------------------------------------------
 
 # Detect Python interpreter — read from identity.json first, fall back to detection