Move make-widget/run-server skills to root .claude/skills/

Nested .claude/skills/ dirs (previously under server/) are only
auto-discovered on-demand once a file under that subdirectory is
touched, so /make-widget and /run-server weren't invocable from a
fresh session. Root .claude/skills/ is scanned at session start.

Fixes setup.sh/start-server.sh's relative cd-depth math (was hardcoded
for the old server/.claude/skills/run-server/ depth) to instead
resolve the repo root via git and cd into server/ explicitly, and
updates SKILL.md/driver.py's path references to match the new layout.

.claude/skills/run-server/start-server.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# Background-launch the server against a scratch DB/config -- never the
+# real deployment's data (see CLAUDE.md). Waits for readiness, prints
+# the PID and log path. Usage: ./start-server.sh [scratch-dir] [port]
+set -euo pipefail
+cd "$(git -C "$(dirname "${BASH_SOURCE[0]}")" rev-parse --show-toplevel)/server"
+
+SCRATCH="${1:-/tmp/run-server-scratch}"
+PORT="${2:-8420}"
+mkdir -p "$SCRATCH"
+
+DATABASE_URL="sqlite:///$SCRATCH/test.db" \
+CONFIG_PATH="$SCRATCH/config.json" \
+.venv/bin/uvicorn app.main:app --host 127.0.0.1 --port "$PORT" \
+  > "$SCRATCH/server.log" 2>&1 &
+PID=$!
+echo "$PID" > "$SCRATCH/server.pid"
+
+for _ in $(seq 1 30); do
+  curl -sf -o /dev/null "http://127.0.0.1:$PORT/" && break
+  sleep 0.5
+done
+
+if ! curl -sf -o /dev/null "http://127.0.0.1:$PORT/"; then
+  echo "server did not become ready -- check $SCRATCH/server.log" >&2
+  exit 1
+fi
+
+echo "server PID $PID up on http://127.0.0.1:$PORT (log: $SCRATCH/server.log, db: $SCRATCH/test.db)"