Add end-to-end timing instrumentation and an xtask benchmark report for mvp-chat runs.
- benchmark_observability: add a shared stamping module — stamp(component) emitting schema/pid/monotonic+wall ms from a process-global start and sequence counter, plus unix_ms_now() — stamped onto every mvp-chat/orchestrator/worker-node event and frame-archive record
- mvp-chat: thread a run_id (new --run-id, defaults to 1) through config and the orchestrator CLI, add per-phase started/ready/failed emits for ensure_orch_binary/ensure_worker_binary/prepare_node_image, and a prompt_complete record carrying tokens_generated/elapsed_ms/final_text bytes
- orchestrator/worker-node: stamp bootstrap and prompt events, add arrival_unix_ms to archived frames, propagate MVP_RUN_ID/MVP_LOGICAL_NODE_ID/MVP_STAGE_INDEX into the tinygrad worker, default the device to CPU for the process provider, emit a prompt_rpc started span, and drop the MVP_TINYGRAD_TEST_MODE passthrough
- tinygrad_worker.py: stamp every control() event and tag it with run/node/stage env, add a CPU:X86 fallback when clang is absent, and remove the test_mode() short-circuits
- xtask: replace the flat dump-log fact assertions with a benchmark report builder (build_benchmark_report) that requires named spans (prepare_runtime, ensure_*_binary, weights_loaded, prompt_rpc) and emits per-prompt first-token/decode/tokens-per-second latency; wrap the cargo run in XtaskBenchmark synthetic frames and pass a unix-ms --run-id
Signed-off-by: Zachery Aaron Shores-Chmielewski <zacheryasc@gmail.com>
