Restore login account removal

[shiny-code-bot]

Finish Line

Users can remove inactive or active login accounts safely, including selecting and committing a replacement app-server thread when required.

Current Status

Deferred from lab.5 by explicit product decision. The release will not restore inactive/active account removal merely to recover pre-alignment parity. Keep this issue parked for post-release dogfood; resume only if observed use justifies the replacement-thread and fallback-account carrying cost. No implementation should land before lab.5 publication or the first post-release convergence checkpoint.

Acceptance Criteria

• Restore account-removal event handling for local and app-server account stores.
• Handle inactive-account removal without unnecessary session replacement.
• Select and activate a safe fallback when removing the active account.
• Restore the shared replacement-thread preparation/commit helper with rollback-safe UI behavior.
• Refresh the accounts view with success or actionable failure feedback.
• Cover active, inactive, last-account, and replacement-failure cases.

Relationships

• Fourth implementation stage of Restore login account management TUI wiring #690.
• Blocked by Restore app-server login account completion #696.
• Blocks account switching because the replacement-thread helper is shared.

Open Questions

• None; preserve the donor flow's rollback semantics exactly.