feat(sbp2): add session registry and command flow

[gly11]

Summary

This PR is stacked on pr/foundation-async-discovery and adds the SBP-2 session and command core on top of the foundation fixes.

SBP-2 Session Core

• Add login, reconnect, and logout session state handling, including bus-reset retry behavior, busy-timeout replay, and unsolicited status setup
• Add a session registry for discovered SBP-2 units and command lifecycle management
• Add command submission helpers for standard SCSI command flow and task management
• Wire SBP-2 session operations through ControllerCore, DriverContext, and the user-client handler

ORB and Addressing

• Extend management and command ORB layout and status handling
• Add full bus/node embedded-address handling and page-table/direct-descriptor updates
• Add command wire formats for the user-client boundary

Tests

• Add login-session and session-registry coverage
• Extend ORB and address-space tests for timeout, status, embedded-address, and command lifecycle behavior

Why this PR

This layer adds SBP-2 session and command behavior without mixing in controller bring-up policy, Swift connector APIs, app UI, local diagnostic scripts, or documentation-only planning notes.

Verification

Local verification completed for this slice:

cmake -S . -B /tmp/asfw-pr19-build -DCMAKE_BUILD_TYPE=Debug
cmake --build /tmp/asfw-pr19-build --target AddressSpaceManagerTests SBP2ORBTests SBP2LoginSessionTests SBP2SessionRegistryTests --parallel 8
/tmp/asfw-pr19-build/tests/AddressSpaceManagerTests
/tmp/asfw-pr19-build/tests/SBP2ORBTests
/tmp/asfw-pr19-build/tests/SBP2LoginSessionTests
/tmp/asfw-pr19-build/tests/SBP2SessionRegistryTests
xcodebuild -project ASFW.xcodeproj -scheme ASFW -configuration Debug -destination 'platform=macOS' CODE_SIGNING_ALLOWED=NO build

[gly11]

Superseded by mrmidi#19, which has been merged. Closing this fork-side draft; follow-up SBP-2 work will be re-split against the current upstream architecture.