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>

docs/DEVOPS.md

@@ -62,11 +62,27 @@ The server must be running before the client connects (subprocess launch will be
 ### Test
 
 ```bash
-make test               # Run all tests
-make test-server        # cargo test in server/
-make test-client        # gdUnit4 tests (headless runner pending)
+make test               # Run all tests (test-server + test-client)
+make test-server        # Rust tests via tests/run-rust (cargo nextest, JSON summary)
+make test-client        # Godot tests via tests/run-godot (gdUnit4 headless, JSON summary)
 ```
 
+The IPC test layers (D-030) have dedicated targets:
+
+```bash
+make test-ipc-fixtures      # Layer 1: serialization round-trip fixtures
+make test-ipc-protocol      # Layer 2: mock LocalBridge protocol tests
+make test-ipc-integration   # Layer 3: real subprocess round-trip (+ benchmark when ready)
+make test-ipc-benchmark     # IPC latency benchmark (blocked: #555/#556 handshake)
+```
+
+Each `tests/run-*` script outputs a JSON summary to stdout and streams progress to stderr:
+```json
+{"suite":"rust","total":42,"passed":42,"failed":0,"duration_ms":1230}
+```
+
+All scripts accept `--filter <name>` to run a subset of tests. They are whitelistable for agent use (no TTY prompts, no interactive input).
+
 Server tests use Rust's built-in test framework with `#[cfg(test)]` inline tests and `tests/` integration tests (D-030). Client tests use gdUnit4 (D-030).
 
 ### Cross-Encoder Fixtures