refactor(e2e): extract infrastructure into tests/e2e/infra/ module

- Move fixtures.ts, llm-judge.ts, results-db.ts to tests/e2e/infra/
- Deduplicate wdio.conf.js: use createTestFixture() instead of inline copy
- Replace __dirname paths with projectRoot-anchored paths
- Create test-mode-constants.ts (typed env var names, flag registry)
- Create scripts/preflight-check.sh (validates tauri-driver, display, Claude CLI)
- Create scripts/check-test-flags.sh (CI lint for AGOR_TEST flag drift)
- Rewrite tests/e2e/README.md with full documentation
- Update spec imports for moved infra files

scripts/check-test-flags.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+# Lint check: verify all AGOR_TEST references are documented.
+# Run in CI to catch flag drift between code and documentation.
+
+set -euo pipefail
+
+echo "Checking AGOR_TEST flag references..."
+
+# Known files that should reference AGOR_TEST (from test-mode-constants.ts)
+KNOWN_FILES=(
+  "agor-core/src/config.rs"
+  "src-tauri/src/commands/misc.rs"
+  "src-tauri/src/lib.rs"
+  "src-tauri/src/watcher.rs"
+  "src-tauri/src/fs_watcher.rs"
+  "src-tauri/src/telemetry.rs"
+  "src/App.svelte"
+  "tests/e2e/wdio.conf.js"
+  "tests/e2e/infra/fixtures.ts"
+  "tests/e2e/infra/test-mode-constants.ts"
+)
+
+# Find all files referencing AGOR_TEST (excluding node_modules, target, .git)
+FOUND=$(grep -rl 'AGOR_TEST' --include='*.rs' --include='*.ts' --include='*.js' --include='*.svelte' \
+  --exclude-dir=node_modules --exclude-dir=target --exclude-dir=.git . 2>/dev/null | \
+  sed 's|^\./||' | sort)
+
+UNKNOWN=""
+for f in $FOUND; do
+  MATCH=0
+  for k in "${KNOWN_FILES[@]}"; do
+    if [[ "$f" == "$k" ]]; then
+      MATCH=1
+      break
+    fi
+  done
+  if [[ $MATCH -eq 0 ]]; then
+    UNKNOWN="$UNKNOWN  $f\n"
+  fi
+done
+
+if [[ -n "$UNKNOWN" ]]; then
+  echo ""
+  echo "WARNING: AGOR_TEST referenced in files not in the known registry:"
+  echo -e "$UNKNOWN"
+  echo "Update tests/e2e/infra/test-mode-constants.ts and this script."
+  exit 1
+else
+  echo "All AGOR_TEST references are documented. ✓"
+fi