Add UTM VM export task and improve macOS Vagrant setup

[DimmKirr]

Changes

• chore(Taskfile): add vagrant:box:export task to export UTM VMs as Vagrant boxes with usage instructions and validations
• chore(Taskfile): set silent true and add TMUX_PANE var to macos tasks for cleaner output and compatibility
• chore(Vagrantfile.local-example): adjust asdf provisioning to always install devcell base tools first, then project tools, merging .tool-versions properly
• chore(Vagrantfile): improve path handling using dirname(FILE), set default MACOS_BOX to devcell-macOS26, increase VM memory and CPUs for better performance
• chore(Vagrantfile): change synced folder mounting for Claude/Codex config to use CELL_HOME as a single mount point with symlinks for config files
• chore(Vagrantfile): set asdf provisioning run to "never" to avoid unintended provisioning runs, keep base provisioners for reference
• chore(Vagrantfile): load Vagrantfile.local from DEVCELL_DIR instead of HOST_PATH for consistency and remove unused else debug output