merge: resolve conflicts with origin/main

- VERSION/package.json: keep v0.3.1
- CHANGELOG: include both v0.3.x entries and v0.0.2 from main
- setup: combine main's smart rebuild logic with our Playwright auto-install
- tests: keep main's CLI server script resolution + dead state file tests,
  fix CONDUCTOR_PORT env leak causing port conflicts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

setup

@@ -13,14 +13,29 @@ ensure_playwright_browser() {
   ) >/dev/null 2>&1
 }
 
-# 1. Build browse binary if needed
+# 1. Build browse binary if needed (smart rebuild: stale sources, package.json, lock)
+NEEDS_BUILD=0
 if [ ! -x "$BROWSE_BIN" ]; then
+  NEEDS_BUILD=1
+elif [ -n "$(find "$GSTACK_DIR/browse/src" -type f -newer "$BROWSE_BIN" -print -quit 2>/dev/null)" ]; then
+  NEEDS_BUILD=1
+elif [ "$GSTACK_DIR/package.json" -nt "$BROWSE_BIN" ]; then
+  NEEDS_BUILD=1
+elif [ -f "$GSTACK_DIR/bun.lock" ] && [ "$GSTACK_DIR/bun.lock" -nt "$BROWSE_BIN" ]; then
+  NEEDS_BUILD=1
+fi
+
+if [ "$NEEDS_BUILD" -eq 1 ]; then
   echo "Building browse binary..."
-  cd "$GSTACK_DIR" && bun install && bun run build
+  (
+    cd "$GSTACK_DIR"
+    bun install
+    bun run build
+  )
 fi
 
 if [ ! -x "$BROWSE_BIN" ]; then
-  echo "gstack setup failed: browse binary not found at $BROWSE_BIN" >&2
+  echo "gstack setup failed: browse binary missing at $BROWSE_BIN" >&2
   exit 1
 fi
 
@@ -57,12 +72,12 @@ if [ "$SKILLS_BASENAME" = "skills" ]; then
   done
 
   echo "gstack ready."
-  echo "  browse: $GSTACK_DIR/browse/dist/browse"
+  echo "  browse: $BROWSE_BIN"
   if [ ${#linked[@]} -gt 0 ]; then
     echo "  linked skills: ${linked[*]}"
   fi
 else
   echo "gstack ready."
-  echo "  browse: $GSTACK_DIR/browse/dist/browse"
+  echo "  browse: $BROWSE_BIN"
   echo "  (skipped skill symlinks — not inside .claude/skills/)"
 fi