feat(sandbox): trace JS dataplane operations

[Mukil Loganathan (langchain-infra)]

Summary

• Trace JS sandbox dataplane operations as LangSmith tool runs for run, reconnect, write, and read
• Attach sandbox_id and sandbox_name metadata to those traces
• Keep command and file payload behavior unchanged: no sandbox id env injection, no env-key logging, and file contents stay out of trace inputs

Test Plan

• pnpm exec tsc --noEmit --pretty false
• pnpm test:single src/tests/sandbox.test.ts
• pnpm exec oxlint src/sandbox/sandbox.ts src/tests/sandbox.test.ts
• pnpm exec oxfmt --check src/sandbox/sandbox.ts src/tests/sandbox.test.ts

[github-actions]

JS perf benchmark

Lower is better. Noisy on shared runners — treat as a signal, not a gate.

Base64-heavy payload

Single large base64 string per message — the shape the worker-offload path is optimized for.
Payload: 2511.2 KB in / 5.2 KB out, 100 runs.

metric	main	this PR	delta
Wall time (ms)	2144.82	1789.38	-16.6%
createRun total (ms)	95.25	93.40	-1.9%
createRun p50 (ms)	0.64	0.75	+16.1%
createRun p95 (ms)	0.93	1.00	+7.6%
createRun p99 (ms)	36.05	31.81	-11.8%
createRun max (ms)	36.05	31.81	-11.8%
updateRun total (ms)	44.39	55.53	+25.1%
updateRun p95 (ms)	0.89	2.72	+205.2%
loop lag total (ms)	899.11	959.71	+6.7%
loop lag p50 (ms)	0.09	0.10	+4.6%
loop lag p95 (ms)	4.13	5.21	+26.1%
loop lag p99 (ms)	12.13	29.82	+145.8%
loop lag max (ms)	121.88	95.27	-21.8%

Structural payload

Many small strings across a wide/nested object graph. Should bypass worker offload and use sync flush.
Payload: 1239.5 KB in / 13.3 KB out, 100 runs.

metric	main	this PR	delta
Wall time (ms)	1500.27	1453.69	-3.1%
createRun total (ms)	454.33	404.44	-11.0%
createRun p50 (ms)	3.38	3.38	-0.0%
createRun p95 (ms)	13.45	6.16	-54.2%
createRun p99 (ms)	27.23	17.28	-36.5%
createRun max (ms)	27.23	17.28	-36.5%
updateRun total (ms)	29.96	28.74	-4.1%
updateRun p95 (ms)	0.55	0.54	-1.7%
loop lag total (ms)	1057.51	1017.98	-3.7%
loop lag p50 (ms)	0.07	0.07	+1.7%
loop lag p95 (ms)	4.86	4.94	+1.6%
loop lag p99 (ms)	124.47	124.18	-0.2%
loop lag max (ms)	129.10	147.57	+14.3%