ci: share one platform run across matrix jobs via --run-key

[HeyGarrison]

Updates the matrix benchmark workflows to pass a shared RUN_KEY (${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT}) to every bench run invocation, so all provider matrix jobs for a given workflow run join the same platform run. runKey is still scoped by benchmark slug, so distinct slugs (e.g. TTI shapes) still get distinct runs.

• snapshot-fork-benchmarks.yml
• browser-benchmarks.yml
• browser-throughput-benchmarks.yml
• sandbox-dax-benchmarks.yml
• storage-benchmarks.yml: storage.bench.ts hardcodes benchmarkSlug: 'storage-local', so RUN_KEY also includes the matrix FILE_SIZE to keep each file size in its own run while still grouping all providers per size.

Skipped:

• sandbox-tti-benchmarks.yml — already passes --run-key.
• ai-gateway-benchmarks.yml — deliberately a single job (no matrix) per its own comment.
• git-benchmarks.yml — not present in this repository.

Note: pnpm typecheck currently fails on benchmarks/sandbox/tti.bench.ts(64,3) (shapes not in BenchmarkConfig) on master as well, so that failure is pre-existing and unrelated to these workflow changes.

Link to Devin session: https://app.devin.ai/sessions/303937628eab4d9f874312edc3a02b88
Requested by: @HeyGarrison

---

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring

[open-cla]

Contributor License Agreement

All contributors are covered by a CLA.

[devin-ai-integration]

Devin Review found 1 potential issue.