cmd/docker: print command error before running plugin hooks

[adisivaprasad]

- What I did

Fixes #6973 — when a command fails and a plugin error-hook (or hook) produces a "What's next" hint, the hint was printed before the command's error message:

$ docker run --rm --env-file=./no-such-file alpine

What's next:
    Debug this container error with Gordon → docker ai "help me fix this container error"
docker: open ./no-such-file: no such file or directory

Run 'docker run --help' for more information

- How I did it

The cobra tree runs with SilenceErrors: true, so the error is only printed by main() after runDocker() returns, while plugin hooks run inside runDocker() right after cmd.ExecuteContext() — hence the inverted order.

In runDocker(), before invoking the hooks I now print the pending (non-canceled, non-silent) command error to stderr, and replace the returned error with a bare cli.StatusError carrying the exit code only, so main() doesn't print it a second time. Canceled and signal-terminated errors (which print nothing) pass through untouched, and exit codes are unchanged.

- How to verify it

Repro for that area is in the issue. I verified end-to-end with a stub hook plugin (docker-demo CLI plugin answering docker-cli-plugin-hooks with a fixed next-steps template) configured with "error-hooks": "run", DOCKER_CLI_HOOKS=true, under a pty:

Before (current master build):

$ docker run --rm --env-file=./no-such-file alpine

What's next:
    Try the --debug flag to diagnose (fake hook hint)
docker: --env-file: open ./no-such-file: no such file or directory

Run 'docker run --help' for more information

After (this patch):

$ docker run --rm --env-file=./no-such-file alpine
docker: --env-file: open ./no-such-file: no such file or directory

Run 'docker run --help' for more information

What's next:
    Try the --debug flag to diagnose (fake hook hint)

• Exit code is 125 both before and after (same as unpatched).
• Success-case hooks still print after command output (verified with a hooks: context config on docker context ls).
• go test ./cmd/docker/... ./cli-plugins/... passes.

Fixed plugin hook messages (e.g. "What's next" hints) being printed before the command's error message when a command fails