fix: align browser accessibility public contract

[chubes4]

Summary

• add the intentional browser-accessibility module to the manually maintained public and contracts barrel expectations
• verify the accessibility schema and contract helper remain exported from the root compatibility barrel, curated public facade, and contracts facade
• preserve the package export map and public surface introduced by Add browser accessibility, keyboard, and focus fuzzing oracles #2065 without adding new exports or infrastructure

browser-accessibility is intentional because #2065 added it to all three core facades alongside the adaptive browser contract and runtime-playground collector that consume it. This PR only restores contract-test parity with that existing surface.

Testing

• npm run build
• npm run test:public-api-contract
• npm run test:runtime-contract-manifest
• npm run test:runtime-contract-package-exports
• npm run test:schema-parity
• npm run test:browser-accessibility-oracles (42 passed)
• npm run test:release-package-coverage
• npm run check (reaches the existing command-registry-smoke fails on main: wordpress.collect-workload-result outputShape missing outputSchema id mention #1745 baseline failure in command-registry-smoke: wordpress.collect-workload-result outputShape should mention outputSchema id; production boundary enforcement and all preceding smoke checks pass)

Fixes #2075