Build a UEFI BDS semantic parity matrix for patina_boot

[kat-perez]

Parent: #190

Goal

Make supported behavior and intentional policy differences explicit relative to EDK2 BdsDxe/UefiBootManagerLib.

Coverage

• BootOrder, BootNext, BootCurrent, active/inactive and duplicate options
• OptionalData and maximum-size variables
• Driver, SysPrep, Boot, and PlatformRecovery option categories
• EndOfDxe, ReadyToBoot, Before/AfterConsole, and platform event ordering
• watchdog, console, OS indications, deferred images, and failure behavior

Acceptance criteria

• matrix labels each behavior supported, platform-policy, intentionally unsupported, or planned
• every supported row links to a host, QEMU, or hardware test
• upstream API documentation defines compatibility expectations
• OEMs can identify migration gaps without reading implementation source

[kat-perez]

Started in Iteration 10. The initial source-grounded matrix is drafted at uefi/crates/patina_boot/docs/uefi-bds-semantic-parity.md and linked from the crate README. The first pass identifies security-transition ordering, BootNext/BootCurrent, OptionalData, OsIndications, non-Boot option categories, short-form partition identity, and fallback-source policy as the principal compatibility decisions.