v1.158.0 cannot parse config files it writes — "yaml: line 2228: did not find expected key"

## Summary

doctl `v1.158.0` (released 2026-05-07 16:21 UTC) cannot read its own config files. Every doctl invocation fails at startup with:

```
doctl: 2026/05/07 21:08:20 Config initialization failed: While parsing config: yaml: line 2228: did not find expected key
```

`v1.157.0` reads the **same file** successfully — verified.

## Reproduction

1. Install doctl v1.158.0
2. Run any doctl command (auth init, auth list, registry login, etc.)
3. The first invocation may write a default config (37,883 bytes / 2,227 lines on Linux x86_64); subsequent invocations fail to read it.

The error appears at line 2228 of a 2227-line file — i.e., doctl's parser expects more YAML content than the writer produced. The file ends mid-section with `vpcs.update.name: ""`.

## Evidence the file itself is valid YAML

`yaml.safe_load` (PyYAML) parses the file successfully:
- 91 top-level keys
- Well-formed structure (1-click, access-token, account, action, activations, agent, alert, api-url, apikeys, apps, ...)

So the failure is in doctl's parser, not the file.

## Evidence v1.157.0 reads the same file

```bash
$ wget https://github.com/digitalocean/doctl/releases/download/v1.157.0/doctl-1.157.0-linux-amd64.tar.gz
$ tar xf doctl-1.157.0-linux-amd64.tar.gz
$ ./doctl --config=/home/USER/.config/doctl/config.yaml auth list
default (current) # <-- success on the same file v1.158.0 fails on
```

## Suspected commit

The v1.157.0 → v1.158.0 changelog has only 2 commits:

- [#1835 DOKS SSO: per-cluster config, kubeconfig type](https://github.com/digitalocean/doctl/pull/1835) — explicitly modifies config schema structure
- [#1839 Bump godo to v1.189.0](https://github.com/digitalocean/doctl/pull/1839) — internal HTTP client only, unlikely cause

#1835 is the prime suspect — config schema additions can produce serialization output that the parser doesn't expect.

## Impact

- All CI runs using `digitalocean/action-doctl@v2` (which defaults to `version: 'latest'`) broke today within hours of the v1.158.0 release.
- Workaround: pin to `version: '1.157.0'` in workflow input.
- Long-term users with shared doctl config homes (e.g., self-hosted runners) are affected even after pinning, since the broken file persists until manually cleared. v1.157.0 reads the v1.158.0-written file fine, so the workaround does not require config cleanup.

## Environment

- doctl: v1.158.0
- OS: Ubuntu (self-hosted GitHub Actions runner, Linux x86_64)
- Action: `digitalocean/action-doctl@v2` with `version: 'latest'` (default)

## Workaround applied on our side

Pinning `version: '1.157.0'` in all `digitalocean/action-doctl@v2` callsites until v1.159.0 (or v1.158.x) ships a fix.

Happy to provide the corrupted config file (with secrets redacted) on request.