Accept alpha.7 tester build

[R055LE]

What changed

• record alpha.7 as the current accepted signed tester build
• document physical acceptance of retained-session Home and Return
• document drafting a follow-up while a command runs, including disabled Send until the shell is ready
• keep command queuing and concurrent sessions explicitly deferred
• update release-signing history without rewriting alpha.6 evidence

Why

The signed alpha.7 build is installed on the owner device and both new feature paths have passed physical acceptance. The repository should no longer describe alpha.6 as current or alpha.7 as awaiting validation.

Impact

Tester-facing status now matches the installed accepted build. No application code changed.

Checks

• physical alpha.7 Home, Return, and drafting acceptance on Galaxy S25 Ultra
• git diff --check
• staged secret and endpoint-pattern scan