chore: address post-merge NUT review comments (W-23400737)

[jhefferman-sfdc]

What & why

Follow-up to #676 (W-23400737), addressing the two actionable review comments left after that PR merged:

1. getAccessToken no longer exported (browserUtils.ts:31) — per @wjhsf, it's only referenced within browserUtils.ts (by getPreview), so the export was unnecessary.
2. Number.parseInt → global parseInt (sessionUtils.ts:28) — per @wjhsf, for consistency with the rest of the repo, which uses global parseInt/parseFloat throughout (src/configMeta.ts, src/shared/previewUtils.ts, and devServerUtils.ts in this same helper dir).

Both are test-helper-only, no behavior change. Lint + tsc + pre-commit hooks pass locally.

Not addressed (already resolved on #676)

• @rax-it's "should we try a default version?" on getMaxSupportedApiVersion was answered inline and the PR was subsequently approved — fail-fast is intentional (an empty apiVersionMetadata means the plugin is misconfigured; the shipping dependencyLoader.ts reads the same map and would break too, and there's no canonical default version constant to fall back to).
• @wjhsf's design question ("what happens when the platform gets a new default API version but this package isn't updated?") is exactly the drift this fix is designed to absorb: the tests pin the preview to the plugin's own max supported version rather than the org's, so they stay green until a human adds the new version to apiVersionMetadata (+ its @lwc/sfdx-local-dev-dist-<v> dist). Adding real support for a newer API version remains a separate product task, by design.

@W-23400737@