feat: install.sh + auto-update checker for CLI

- tools/install.sh: standalone installer/upgrader, curl-pipe safe
  (main() wrapper, process.argv instead of stdin, mkdir -p prefix)
- packages/mosaic/src/runtime/update-checker.ts: version check module
  with 1h cache at ~/.cache/mosaic/update-check.json
- CLI startup: non-blocking background update check on every invocation
- 'mosaic update' command: explicit check + install (--check for CI)
- session-start.sh: warns agents when CLI is outdated
- Proper semver comparison including pre-release precedence
- eslint: allow __tests__ in packages/mosaic for projectService

scripts/agent/session-start.sh

@@ -8,6 +8,18 @@ source "$SCRIPT_DIR/common.sh"
 ensure_repo_root
 load_repo_hooks
 
+# ─── Update check (non-blocking) ────────────────────────────────────────────
+if command -v mosaic &>/dev/null; then
+  if mosaic update --check 2>/dev/null; then
+    : # up to date
+  elif [[ $? -eq 2 ]]; then
+    echo ""
+    echo "[agent-framework] ⚠ A newer version of Mosaic CLI is available."
+    echo "[agent-framework]   Run: mosaic update  or  bash tools/install.sh"
+    echo ""
+  fi
+fi
+
 if git rev-parse --is-inside-work-tree >/dev/null 2>&1 && has_remote; then
   if git diff --quiet && git diff --cached --quiet; then
     run_step "Pull latest changes" git pull --rebase