Finish Herdr and Scatterer configuration

[RestartDK]

Summary

Follow-up to #69 containing the remaining local configuration changes:

• customize Herdr's agent sidebar, sorting, and Kitty graphics support
• update the twin Pi model defaults
• update the Scatterer source and package dependencies/hash, and enable its test suite
• preserve explicit local Scatterer development links while refreshing Nix-store plugin registrations offline
• add tab_close to Pi's Herdr tool and require cleanup of transient processes and work tabs before finishing tasks

Validation

• traitor update scatterer-src
• traitor check
• direct Nix build of the updated Scatterer package (BUILD_STATUS=0)
• npm run typecheck
• npm run check-generated
• live raw-socket tab create/close test
• JSON and TOML parsing