feat: unify mosaic CLI — single binary, no PATH conflict

- Rename framework bash launcher: mosaic → mosaic-launch
- npm CLI (@mosaic/cli) is now the single 'mosaic' binary on PATH
- Add launcher delegation: mosaic {claude,codex,opencode,pi,yolo}
  delegates to mosaic-launch via execFileSync with inherited stdio
- Add delegated management commands: init, doctor, sync, seq,
  bootstrap, coord, upgrade
- install.sh: remove framework bin PATH requirement, clean up old
  mosaic binary on upgrade, simplified summary output
- framework install.sh: preserve sources/ dir (fixes rsync noise
  about agent-skills)
- session-run.sh: update references to mosaic-launch

Users now only need ~/.npm-global/bin on PATH. The npm CLI finds
mosaic-launch at its absolute path (~/.config/mosaic/bin/mosaic-launch).

packages/mosaic/framework/install.sh

@@ -4,7 +4,7 @@ set -euo pipefail
 SOURCE_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 TARGET_DIR="${MOSAIC_HOME:-$HOME/.config/mosaic}"
 INSTALL_MODE="${MOSAIC_INSTALL_MODE:-prompt}" # prompt|keep|overwrite
-PRESERVE_PATHS=("SOUL.md" "USER.md" "TOOLS.md" "memory")
+PRESERVE_PATHS=("SOUL.md" "USER.md" "TOOLS.md" "memory" "sources")
 
 # Colors (disabled if not a terminal)
 if [[ -t 1 ]]; then
@@ -21,7 +21,7 @@ step() { echo -e "\n${BOLD}$1${RESET}"; }
 
 is_existing_install() {
   [[ -d "$TARGET_DIR" ]] || return 1
-  [[ -f "$TARGET_DIR/bin/mosaic" || -f "$TARGET_DIR/AGENTS.md" || -f "$TARGET_DIR/SOUL.md" ]]
+  [[ -f "$TARGET_DIR/bin/mosaic-launch" || -f "$TARGET_DIR/bin/mosaic" || -f "$TARGET_DIR/AGENTS.md" || -f "$TARGET_DIR/SOUL.md" ]]
 }
 
 select_install_mode() {