feat(ci): test runner scripts and Makefile integration (#270)

Six test runner scripts at tests/: run-rust, run-godot, run-ipc-fixtures,
run-ipc-protocol, run-ipc-integration, run-all. Plus run-ipc-benchmark
for Layer 3 timing. All produce structured JSON stdout, support --filter,
and exit 0/non-zero. Makefile targets updated to delegate to scripts.

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

tests/run-rust

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# tests/run-rust: Run Rust test suite via cargo nextest (D-030)
+# Exit: 0 = all pass, non-zero = failure
+# Stdout: {"suite":"rust","total":N,"passed":N,"failed":N,"duration_ms":N}
+set -euo pipefail
+
+FILTER=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --filter) FILTER="${2:-}"; shift 2 ;;
+        --filter=*) FILTER="${1#--filter=}"; shift ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$REPO_ROOT/server"
+
+START_MS=$(date +%s%3N)
+TMPOUT=$(mktemp)
+
+NEXTEST_ARGS=(nextest run --color never)
+if [[ -n "$FILTER" ]]; then
+    NEXTEST_ARGS+=(-E "test(~${FILTER})")
+fi
+
+set +e
+cargo "${NEXTEST_ARGS[@]}" 2>&1 | tee "$TMPOUT" >&2
+EXIT_CODE=${PIPESTATUS[0]}
+set -e
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+# Parse nextest summary: "    Summary [  0.123s] N tests run: X passed[, Y failed], Z skipped"
+# (older nextest uses "Finished", newer uses "Summary" — match both)
+SUMMARY=$(grep -E "^\s*(Summary|Finished)" "$TMPOUT" | tail -1 || true)
+
+_extract_num() {
+    local haystack="$1" pattern="$2"
+    echo "$haystack" | grep -oE "[0-9]+ $pattern" | grep -oE '^[0-9]+' || echo 0
+}
+
+TOTAL=0; PASSED=0; FAILED=0
+if [[ -n "$SUMMARY" ]]; then
+    TOTAL=$(_extract_num "$SUMMARY" "tests? run")
+    PASSED=$(_extract_num "$SUMMARY" "passed")
+    FAILED=$(_extract_num "$SUMMARY" "failed")
+fi
+
+rm -f "$TMPOUT"
+printf '{"suite":"rust","total":%d,"passed":%d,"failed":%d,"duration_ms":%d}\n' \
+    "${TOTAL:-0}" "${PASSED:-0}" "${FAILED:-0}" "$DURATION_MS"
+exit $EXIT_CODE