Implement the upstream patina_boot semantic baseline

[kat-perez]

Parent roadmap: #190

Goal

Implement the UEFI BDS semantic baseline accepted for upstream patina_boot after the #196 parity review.

Scope

• turn every planned row selected for the upstream contract into code and tests
• cover the agreed handling of BootNext, BootCurrent, OptionalData, option categories, and relevant OS indications
• preserve explicit platform-policy extension points instead of importing product-specific EDK2 behavior
• update API documentation and the parity matrix as behavior lands

Acceptance criteria

• maintainers approve the upstream semantic baseline derived from Build a UEFI BDS semantic parity matrix for patina_boot #196
• every supported row has a host, QEMU, or hardware test
• unsupported and platform-policy rows remain explicit
• no generic API requires Maa- or vendor-specific policy
• the parity matrix contains no unexplained partial behavior in the upstream contract

Dependencies

• Blocked by Build a UEFI BDS semantic parity matrix for patina_boot #196
• Coordinates with Make the BDS security transition fail closed #191 and Harden patina_boot device-path and boot-source selection #192