SMSTunnel command-line tool

Help me write a script that sends text messages with the SMSTunnel command-line tool.

About SMSTunnel (https://smstunnel.io): my own apps and tools hand text messages (SMS) to my SMSTunnel account, and my own Android phone sends them from my own number, on my own SIM and plan. The phone runs the SMSTunnel app from Google Play (https://play.google.com/store/apps/details?id=io.smstunnel.app), signed in to my account.

What I want: [describe what should send a text, to whom, and when]

How it works:
- Install the smstunnel command: Windows: Scoop (scoop bucket add smstunnel https://github.com/narcisbodea/smstunnel-cli, then scoop install smstunnel/smstunnel); macOS and Linux: Homebrew (brew tap narcisbodea/smstunnel-cli https://github.com/narcisbodea/smstunnel-cli, then brew install --cask smstunnel); Ubuntu and other Linux (x64): snap (sudo snap install smstunnel); Go 1.24 or newer (go install github.com/narcisbodea/smstunnel-cli/cmd/smstunnel@latest); or the .deb, .rpm or archive for my system from https://github.com/narcisbodea/smstunnel-cli/releases.
- The key comes from the SMSTUNNEL_API_KEY environment variable (in CI, a secret), or from smstunnel login, which reads it from standard input, checks it and saves it in the system keychain. It never goes on the command line.
- smstunnel send <number> <text> [--phone <id or name>] [--country +44] [--wait [--timeout 120]] [--idempotency-key <key>] [--json]. With no text, or -, it reads the text from standard input.
- smstunnel code <number> <text> is for sign-in codes only: the text must contain the code, 4 to 10 digits standing on their own (482913) or 123-456, at most 320 characters. Codes have their own daily allowance.
- smstunnel status <message id>, smstunnel phones, smstunnel usage, smstunnel received [--since 2h] [--from <number>] [--watch]. Reading received texts needs a key with "Can also read received texts" and "Sync received texts" turned on in the app.
- One number per command: to text several people, run it once per number. Numbers in international format (+14155550123); --country completes a number written without + or 00. Texts up to 1600 characters; 30 send requests a minute per key.
- Exit codes: 0 done (also "not confirmed by your phone": most likely sent, never send it again); 1 unexpected; 2 bad input (400) or an idempotency key reused for another text (422); 3 key missing or refused (401); 4 not allowed for this key or plan (403); 5 not found (404); 6 too many requests (429: wait the seconds it says), the plan's limit for the day or month reached (429 without Retry-After), or the same --idempotency-key still in progress (409); 7 SMSTunnel unreachable or a 5xx (the text may have gone out: rerun only with the same --idempotency-key, which never sends a second text; after a 5xx the same key gives the same answer for 24 hours, so check the dashboard's Messages first); 8 the text failed (--wait); 9 still waiting for the phone when --wait gave up (it goes out when the phone is back: don't resend). With --json, the result is JSON on stdout and errors are JSON on stderr: {"error":{"message","exitCode","status"}}.
- Give each text its own --idempotency-key (such as order-1042-ready): running the same command again within 24 hours gets the first answer back instead of a second text. The CLI never resends a text by itself.
- If my phone is offline, the text waits and goes out when the phone is back online, within 3 days.
- The API key comes from my SMSTunnel dashboard (https://dashboard.smstunnel.io): Apps → Add an app → Create the key. It is shown only once and can send texts and check whether they went out.

Rules for your answer:
- Keep the API key in an environment variable or the platform's secret store (for example SMSTUNNEL_API_KEY). Never put it in source code, in a repository, or in code that runs in a browser or a mobile app: call SMSTunnel from a server. I will not paste my key in this chat; use a placeholder.
- Validate phone numbers before sending (international format, like +14155550123) and skip or report the invalid ones.
- Handle errors: log or show what went wrong, retry only after 429, 5xx or network errors and only a few times, and never send the same text twice.
- Only send texts people expect from me: alerts to myself, reminders, sign-in codes, updates they asked for. No unsolicited texts.
- Check the exit code of every command, and never print the key or pass it as an argument.