chore(release): prepare 0.5.0

[moonyue-w]

Summary

Prepare version 0.5.0 for the merged Forward SAT management and Realtime Beta APIs. Align package metadata and current version examples, move the existing release notes into 0.5.0, and retain an empty Unreleased section. Document that Realtime SA access requires a Forward-issued bound SAT and a Realtime-enabled Template.

Why

The release workflow validates the requested version against the source metadata and extracts the matching changelog section. These changes make the merged features ready for the 0.5.0 release.

Verification

• npm run build
• npm run typecheck
• npm test: 3676 passed
• npm run docs:check
• Relevant examples run or import successfully (not rerun; examples unchanged)
• Account-backed integration tests run, or not required: prior feature validation covers base 1e374cdca56692e24470bce0f83990f7480fddb1; no business implementation changed here.

npm pack and npm publish --dry-run passed with npm 12.0.2. Installed the tarball in an independent consumer and verified version 0.5.0, CommonJS/ESM imports, Forward/Managed subpaths, and SAT/Realtime entry points. Dry-run does not validate actual OIDC publishing. Changelog validation, release-note extraction, and all 19 release-script tests passed. No dependency versions changed.

Impact

• Public API or behavior changed
• User-facing changelog updated: release preparation moves existing entries from Unreleased to 0.5.0.
• CommonJS, ESM, and subpath exports remain valid
• Generated API documentation updated: VERSION literal is now 0.5.0
• Contract or wire-field fixtures updated (not required)
• Go and Python parity considered: coordinated 0.5.0 preparation
• Migration notes added for a breaking change (not required)
• No credentials, .env.live, logs, or generated test output committed

This PR changes release metadata and documentation only; it does not change API behavior, retry policy, or test assertions. No new contract fixtures or migration instructions are needed for this version preparation. Live validation was performed against the feature baseline before the version bump; local package checks do not replace public-registry verification after publishing.

Intermittent Realtime service timeouts and transcription/connection failures were observed during earlier live runs. Subsequent runs passed; this version preparation does not claim those service issues are fixed.