test: stabilize parallel provider scenarios

[thymikee]

Summary

Stabilizes parallel provider and interaction-contract tests by isolating mock advisory device claims per Vitest worker and applying a narrow 10s timeout only to the measured contention-prone scenarios.

Replaces the Cloud WebDriver loopback fixture with an in-memory Fetch transport, so sandboxed and concurrent agents retain request/response coverage without binding a local port.

Stacked on #1495.

Validation

pnpm check:affected --base origin/agent/simplify-screenshot-diff --run passed (68 tests). Cloud WebDriver runtime and adapter scenarios also pass in the sandbox without listen EPERM.

[github-actions]

Size Report

Metric	Base	Current	Diff
JS raw	1.87 MB	1.90 MB	+34.1 kB
JS gzip	601.6 kB	611.2 kB	+9.7 kB
npm tarball	720.2 kB	730.2 kB	+10.0 kB
npm unpacked	2.52 MB	2.56 MB	+34.0 kB

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	27.5 ms	27.6 ms	+0.1 ms
CLI --help	57.7 ms	57.9 ms	+0.2 ms

Top changed chunks:

Chunk	Raw diff	Gzip diff
dist/src/png-worker-contract.js	+30.6 kB	+9.4 kB
dist/src/runtime.js	+8.5 kB	+2.6 kB
dist/src/recording-export-quality.js	+2.8 kB	+931 B
dist/src/agent-device-client.js	-164 B	-88 B
dist/src/session.js	0 B	-57 B

[thymikee]

Delta review at 1afbb47 is clean: worker-scoped claim roots preserve advisory-claim behavior while removing cross-fork contention; the in-memory WebDriver fixture still exercises production Fetch request/response handling without a loopback socket; and the narrow 10s exceptions stay below the 15s integration budget. Exact-head static/integration/mutation gates are green, with remaining CI still running. This PR is not independently merge-ready or labelable yet because it is stacked on #1495, whose released-API compatibility finding remains unresolved.

[github-actions]

PR Preview Action v1.8.1
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2026-07-30 12:41 UTC