[konwolters]

Summary

Update the blocked-number contract documentation for the coordinated
secondary-user call-blocking implementation:

• Full secondary users maintain independent call-blocking lists.
• The secondary user's list does not block SMS/MMS or inherit other users' lists.
• Emergency callback suppression is device-wide.
• Existing system/main-user message-blocking behavior remains unchanged.

This PR changes documentation only and belongs with the companion provider,
Telecom, Dialer and manifest changes; it does not independently enable the feature.

Provider implementation:
konwolters/platform_packages_providers_BlockedNumberProvider#1

Checks

Java syntax parsing and whitespace checks.

Related: GrapheneOS/os-issue-tracker#5499, GrapheneOS/os-issue-tracker#5203,
GrapheneOS/os-issue-tracker#5569.

Companion PRs

• Provider implementation/review (contributor repository): Enable independent call blocking for full secondary users konwolters/platform_packages_providers_BlockedNumberProvider#1
• Telecom selection, contacts and management UI: Use secondary users' own call-blocking lists and contacts platform_packages_services_Telecomm#27
• Dialer confirmations and migration UI: Describe secondary-user number blocking as calls-only platform_packages_apps_Dialer#65
• Framework contract documentation: Document independent call-blocking lists for secondary users #475
• Complete provider source integration in the manifest: Select a BlockedNumberProvider fork for secondary-user call blocking platform_manifest#106

These PRs form one coordinated change. The provider review is in a contributor
repository because the GrapheneOS-owned provider fork is not yet publicly available.
That upstream fork must be made available with the implementation before the
manifest switch is merged. The official manifest change does not point to a
personal repository.