merge origin/main into feat/wf5-securestorage

Brings MOSAIC_GIT_IDENTITY (per-seat git authorship) onto the delivery
branch, which had none of it. The branch carried W-F7's FLEET_SEAT seam in
the same launcher file; the two auto-merged cleanly.

Three single-hunk conflicts resolved:
- pr-merge.sh: kept branch policy allowing main OR next (next is the
  release stream).
- test-ci-queue-wait-tristate.sh: kept the branch's 4 added merge-readiness
  assertions; merge base and main both had zero, so nothing of main's is
  reverted.
- package.json test:framework-shell: union of both enumerations, 50 entries,
  no test dropped from either side. Picks up main's test-start-agent-session.sh
  and test-fleet-units.sh, which are the guards for the identity key.

tools/install.sh

@@ -405,13 +405,17 @@ ensure_monorepo() {
     exit 1
   fi
 
-  # Gitea archives extract to <repo-name>/ inside the work dir
-  EXTRACTED_DIR="$(find "$WORK_DIR" -maxdepth 1 -mindepth 1 -type d | head -1)"
-  if [[ -z "$EXTRACTED_DIR" ]] || [[ ! -d "$EXTRACTED_DIR" ]]; then
-    fail "Could not locate extracted source in archive."
+  # Gitea archives extract to exactly one <repo-name>/ inside the work dir.
+  # Read the complete population so a malformed multi-root archive reaches the
+  # named diagnostic instead of aborting on an upstream SIGPIPE under pipefail.
+  local -a extracted_dirs=()
+  mapfile -d '' -t extracted_dirs < <(find "$WORK_DIR" -maxdepth 1 -mindepth 1 -type d -print0)
+  if [[ "${#extracted_dirs[@]}" -ne 1 ]] || [[ ! -d "${extracted_dirs[0]:-}" ]]; then
+    fail "Could not locate exactly one extracted source directory in archive."
     ls -la "$WORK_DIR" >&2
     exit 1
   fi
+  EXTRACTED_DIR="${extracted_dirs[0]}"
 }
 
 # Build @mosaicstack/mosaic + @mosaicstack/gateway from source and install both