feat(josh-sync): add rename command for safe target renames

Adds `josh-sync rename <target>` (PE-12): safely rename a sync target's
name, subfolder, and/or subrepo_url in one resumable operation, editing
.josh-sync.yml and migrating its state-branch files atomically instead of
orphaning them. Bumps josh-sync to v2.3.0.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TNXgcFWVgSh3wkQS55cCX6

lib/state.sh

@@ -73,3 +73,89 @@ write_state() {
 
   git worktree remove "$tmp_dir" 2>/dev/null || rm -rf "$tmp_dir"
 }
+
+# ─── Target-Prefix Migration (used by `rename`) ────────────────────
+# Generic helpers over the whole "<target_name>/" directory on the state
+# branch — agnostic to which command wrote the individual files inside it
+# (this file's per-branch state, or onboard.sh's onboard.json/adopt.json).
+
+# List every path under <target_name>/ on the freshly-fetched state branch.
+# One relative path per line (e.g. "billing/main.json"); empty if none —
+# including when the state branch doesn't exist yet at all.
+state_list_target_files() {
+  local target_name="$1"
+  git fetch origin "$STATE_BRANCH" 2>/dev/null || true
+  git rev-parse -q --verify "origin/${STATE_BRANCH}" >/dev/null 2>&1 || return 0
+  git ls-tree -r --name-only "origin/${STATE_BRANCH}" -- "${target_name}/" 2>/dev/null
+}
+
+# Move every file under <old_name>/ to <new_name>/ (basename preserved), and
+# — when new_filter is non-empty — force `.last_forward.josh_filter` to
+# new_filter in each moved JSON file that has that key (whatever value it
+# currently holds; we don't need to know the prior value, which keeps this
+# safe to re-run mid-rename after the config has already been edited).
+# Files without that key (e.g. onboard.json) pass through untouched. Both
+# the move and the content rewrite land in ONE commit + push.
+#
+# No-op (returns 0, no commit) if <old_name>/ has no files.
+# Dies before mutating anything if any destination path already exists.
+#
+# Usage: state_migrate_target_prefix <old_name> <new_name> [new_filter]
+state_migrate_target_prefix() {
+  local old_name="$1" new_name="$2" new_filter="${3:-}"
+  local files
+  files=$(state_list_target_files "$old_name")
+  [ -n "$files" ] || return 0
+
+  local tmp_dir
+  tmp_dir=$(mktemp -d)
+  git worktree add "$tmp_dir" "origin/${STATE_BRANCH}" 2>/dev/null \
+    || { rm -rf "$tmp_dir"; die "Failed to check out ${STATE_BRANCH}"; }
+
+  # The migration itself runs in a subshell so a mid-flight `exit` (from a
+  # collision `die`, or any unexpected failure) can't skip the worktree
+  # cleanup below. Its exit status is captured explicitly and re-raised via
+  # an unconditional `exit` — relying on the caller's `set -e` to propagate a
+  # failure out of a subshell is NOT reliable (e.g. bats' `run` disables
+  # errexit while capturing output), so this must not depend on it.
+  local migrate_status=0
+  (
+    cd "$tmp_dir" || exit 1
+    local f base dest
+
+    # Pre-flight collision check across all files before mutating anything.
+    while IFS= read -r f; do
+      [ -n "$f" ] || continue
+      base="${f#"${old_name}"/}"
+      dest="${new_name}/${base}"
+      if [ "$f" != "$dest" ] && [ -e "$dest" ]; then
+        die "Destination '${dest}' already exists on ${STATE_BRANCH} — refusing to overwrite"
+      fi
+    done <<< "$files"
+
+    while IFS= read -r f; do
+      [ -n "$f" ] || continue
+      base="${f#"${old_name}"/}"
+      dest="${new_name}/${base}"
+      if [ "$f" != "$dest" ]; then
+        mkdir -p "$(dirname "$dest")"
+        git mv "$f" "$dest"
+      fi
+      if [ -n "$new_filter" ]; then
+        jq --arg new "$new_filter" \
+          'if has("last_forward") and (.last_forward | has("josh_filter")) then .last_forward.josh_filter = $new else . end' \
+          "$dest" > "${dest}.tmp" && mv "${dest}.tmp" "$dest"
+        git add "$dest"
+      fi
+    done <<< "$files"
+
+    if ! git diff --cached --quiet 2>/dev/null; then
+      git -c user.name="$BOT_NAME" -c user.email="$BOT_EMAIL" \
+        commit -m "state: rename ${old_name} -> ${new_name}"
+      git push origin "HEAD:${STATE_BRANCH}" \
+        || die "Failed to push state migration for ${old_name} -> ${new_name}"
+    fi
+  ) || migrate_status=$?
+  git worktree remove "$tmp_dir" 2>/dev/null || rm -rf "$tmp_dir"
+  [ "$migrate_status" -eq 0 ] || exit "$E_GENERAL"
+}