stats: restore terminal when streaming is interrupted by a signal

[Otoru]

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Motivation and Context

When container stats runs in streaming mode, pressing Ctrl+C sends SIGINT directly to the process before Swift can run the defer block responsible for restoring the terminal. This leaves the alternate screen buffer active and the cursor hidden after exit.

Fix this by wrapping the streaming loop in a withThrowingTaskGroup that races the work against an AsyncSignalHandler for SIGINT and SIGTERM. When a signal arrives, the group is cancelled through normal Swift unwinding, allowing the defer to execute and restore the terminal correctly. This follows the same pattern used in BuildCommand.

runStreaming, collectStats, printStatsTable, and clearScreen are promoted to static methods since none of them read instance state, which is required to safely capture only the containers value in the task closure under Swift 6 strict concurrency.

Fixes #1351

Testing

• Tested locally
• Added/updated tests
• Added/updated docs

[dcantah]

@Otoru We require all commits be signed (gpg/ssh)

[Otoru]

@dcantah, thanks for explaining. Fixed.

[dcantah]

@Otoru Can you remove the unit tests? We can add separately

[Otoru]

@dcantah of course