Increment 0: add XCTest target, testing process & 10x value plan

- Add TopManagerTests unit-test target (hosted, @testable import)
- 14 baseline tests for formatters and model math (all green)
- scripts/test.sh build+test loop driver
- docs/TESTING.md (5-gate process), docs/VALUE_PLAN.md (10x rubric)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/test.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+# Fast build+test loop driver for TopManager.
+# Usage:
+#   scripts/test.sh build   # compile only (fast gate)
+#   scripts/test.sh test    # compile + run unit tests
+#   scripts/test.sh         # same as "test"
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+ACTION="${1:-test}"
+DEST='platform=macOS,arch=arm64'
+COMMON=(-project TopManager.xcodeproj -scheme TopManager -configuration Debug -destination "$DEST" CODE_SIGNING_ALLOWED=NO)
+
+case "$ACTION" in
+  build)
+    xcodebuild "${COMMON[@]}" build 2>&1 | tail -20
+    ;;
+  test)
+    xcodebuild "${COMMON[@]}" test 2>&1 \
+      | grep -E "Test Suite|Executed|error:|warning:.*unused|BUILD|TEST (SUCCEEDED|FAILED)|failed \(" \
+      | tail -40
+    ;;
+  *)
+    echo "unknown action: $ACTION" >&2; exit 2 ;;
+esac