NuGet Dependabot container dies with a generic error

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Package ecosystem

NuGet

### Package manager version

_No response_

### Language version

C#, .NET 8

### Manifest location and content before the Dependabot update

_No response_

### dependabot.yml content

```yaml
version: 2

registries:
crb-cos-feed:
type: nuget-feed
url: https://pkgs.dev.azure.com/***redacted***/_packaging/cos/nuget/v3/index.json
token: PAT:${{SYSTEM_ACCESSTOKEN}}
crb-common-feed:
type: nuget-feed
url: https://pkgs.dev.azure.com/***redacted***/_packaging/common/nuget/v3/index.json
token: PAT:${{SYSTEM_ACCESSTOKEN}}

updates:
- package-ecosystem: 'nuget'
labels: ['dependencies']
# Central Package Management manifest lives under Cos/, not the repo root.
directory: '/Cos'
schedule:
interval: 'weekly'
target-branch: 'develop'
registries:
- crb-cos-feed
- crb-common-feed
open-pull-requests-limit: 100
commit-message:
prefix: 'NO-JIRA'
include: 'scope'
# Exactly two groups => at most 2 PRs (one testing, one production).
production catch-all.
groups:
# Test packages
TestLibraries:
patterns:
- 'Microsoft.NET.Test.Sdk'
- 'MSTest*'
- 'Moq'
- 'coverlet.collector'
- 'AutoFixture'
- 'Reqnroll*'
- 'xunit*'
- 'NServiceBus.Testing'
# Everything else - single production PR
ProductionLibraries:
patterns:
- '*'
# Ignore major version upgrades for packages pinned to their current major.
# (revisit when major versions are upgraded or as needed)
ignore:
- dependency-name: 'NServiceBus*'
update-types: ['version-update:semver-major']
- dependency-name: 'Microsoft.Extensions.*'
update-types: ['version-update:semver-major']
- dependency-name: 'System.*'
update-types: ['version-update:semver-major']
- dependency-name: 'Autofac'
update-types: ['version-update:semver-major']
- dependency-name: 'Azure.*'
update-types: ['version-update:semver-major']
- dependency-name: 'AutoMapper'
update-types: ['version-update:semver-major']
- dependency-name: 'EntityFramework'
update-types: ['version-update:semver-major']
- dependency-name: 'NHibernate'
update-types: ['version-update:semver-major']
- dependency-name: 'FluentNHibernate'
update-types: ['version-update:semver-major']
- dependency-name: 'Serilog*'
update-types: ['version-update:semver-major']
- dependency-name: 'AWSSDK.*'
update-types: ['version-update:semver-major']
```

### Updated dependency

_No response_

### What you expected to see, versus what you actually saw

Dependabot completing it's work. Instead, it's crushing in the middle (1 of 2 PRs raised), with an error

```
2026-06-17T15:27:30.9729878Z ##[warning]Free disk space on / is lower than 5%; Currently used: 95.09%
2026-06-17T15:27:32.9710211Z ##[warning]Free disk space on / is lower than 5%; Currently used: 95.09%
2026-06-17T15:27:34.9904847Z ##[warning]Free disk space on / is lower than 5%; Currently used: 95.09%
2026-06-17T15:27:53.8424012Z ##[section]Processing 'record_metrics'
2026-06-17T15:28:29.0663204Z updater | 2026/06/17 15:28:29 ERROR Error type: update_not_possible
2026-06-17T15:28:29.0664000Z - dependencies: - ***redacted***.nRepo.2.6.0
2026-06-17T15:28:29.0709481Z ##[section]Processing 'record_update_job_error'
2026-06-17T15:28:29.0743880Z ##[error]Update)job error: update_not_possible {"dependencies":["Afterman.nRepo.2.6.0"]}
2026-06-17T15:28:29.0746635Z ##[section]Processing 'mark_as_processed'
2026-06-17T15:28:30.3082193Z Failure running container 4cc45395c9e139f0614c160703b3cb6a70662dae63465d9e6660953fd71cfe25: Error: Command failed with exit code 1: /bin/sh -c $DEPENDABOT_HOME/dependabot-updater/bin/run update_files
2026-06-17T15:28:32.3440787Z Cleaned up container 4cc45395c9e139f0614c160703b3cb6a70662dae63465d9e6660953fd71cfe25
2026-06-17T15:28:35.3916284Z Update job 25280272 completed
```

Based on the warning, it seems to be due to AzDO hosted agent running out of space, but it would be good if the error would be logged from the container to indicate Dependabot cannot proceed before the container dies.

### Native package manager behavior

_No response_

### Images of the diff or a link to the PR, issue, or logs

_No response_

### Smallest manifest that reproduces the issue

_No response_

Start with the logged NuGet update_not_possible failure and the preceding low-disk-space warnings, then trace how the updater container reports command failures. Done means the job exposes an actionable error explaining why Dependabot cannot proceed instead of only the generic container exit message.

Written by the indexing model from the issue text.