feat(scripts): merge-settings.sh — jq merge with preservation of theme/editorMode

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/lib/merge-settings.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+# Merge brain settings-fragment.json into consumer's settings.json
+# Replaces: enabledPlugins, permissions, hooks
+# Preserves: theme, editorMode, statusLine, all other keys
+#
+# Usage: merge-settings.sh <consumer-settings.json> <brain-fragment.json>
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+source "$SCRIPT_DIR/common.sh"
+
+target="$1"
+fragment="$2"
+
+require_cmd jq || exit 1
+[ -f "$fragment" ] || { log_error "Fragment not found: $fragment"; exit 1; }
+
+# If target doesn't exist, just copy fragment
+if [ ! -f "$target" ]; then
+    log_info "Target settings.json missing, creating from fragment"
+    cp "$fragment" "$target"
+    exit 0
+fi
+
+# Backup
+backup="${target}.bak.$(date +%s)"
+cp "$target" "$backup"
+
+# Merge: target.* keys preserved EXCEPT enabledPlugins/permissions/hooks — those are REPLACED
+# (not deep-merged) from fragment. Use --slurpfile to load fragment into $frag.
+tmp="${target}.tmp"
+jq --slurpfile frag "$fragment" \
+   '.enabledPlugins = $frag[0].enabledPlugins
+    | .permissions  = $frag[0].permissions
+    | .hooks        = $frag[0].hooks' \
+    "$target" > "$tmp"
+
+# Validate output JSON
+jq empty "$tmp" || { log_error "Merge produced invalid JSON"; rm "$tmp"; exit 1; }
+
+mv "$tmp" "$target"
+log_info "settings.json merged (backup: $backup)"