Prepare Cobb for system-owned Home Manager

[RestartDK]

Summary

• namespace exported dotfiles flake inputs so Cobb can keep its own Home Manager inputs argument
• make the Cobb Daniel module contribute the reusable development package set, Pi/network-namespace wrappers, and live shell/editor config
• remove the Home Manager CLI from shared development modules so concrete system/standalone entry points own activation behavior
• document the single-activator Cobb bridge model

Validation

• ./bin/traitor check
• nix eval --raw .#homeConfigurations.twin.activationPackage.drvPath --no-write-lock-file
• nix eval --raw .#nixosConfigurations.srv-nana.config.system.build.toplevel.drvPath --no-write-lock-file
• evaluated current Cobb main with daniel-dotfiles overridden to this checkout:
  • Daniel home directory: /home/daniel
  • live config: enabled
  • shell config: enabled
  • Twin development environment: enabled
  • Home Manager CLI: disabled
  • titan and titan-2 system toplevels evaluated successfully

Follow-up

A separate Cobb PR will still need to add/pin the daniel-dotfiles input and import homeManagerModules.cobb-daniel from its Daniel profile. This PR intentionally changes only the dotfiles repository.

CI infrastructure note

GitHub Actions jobs are currently prevented from starting because of an account billing/spending-limit issue. The red checks are infrastructure-level; the local and Cobb integration evaluations above passed.

[RestartDK]

CI note: all GitHub Actions jobs were prevented from starting because the account has a billing/spending-limit issue. The failures are infrastructure-level; local and Cobb integration evaluations listed in the PR passed.