Resolves#48988.
I ran `make update-go version=1.26.5`.
- [X] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
## Testing
- [X] QA'd all new/changed functionality manually
Fleet:
<img width="301" height="102" alt="Screenshot 2026-07-09 at 8 41 49 AM"
src="https://github.com/user-attachments/assets/baf76ce7-6192-4506-a9db-52f5318939ee"
/>
fleetctl:
```
fleetctl --version
fleetctl - version orbit-v1.57.0-402-ge3d0c005dc
branch: 48988-update-go-1.26.5
revision: e3d0c005dc6698c024ad47a124c99e4f264855a0
build date: 2026-07-09
build user: lucas
go version: go1.26.5
```
Also verified orbit in Linux:
<img width="582" height="121" alt="Screenshot 2026-07-09 at 8 51 55 AM"
src="https://github.com/user-attachments/assets/65672676-8010-45a1-8c28-9f9959e72134"
/>
## fleetd/orbit/Fleet Desktop
- [X] Verified compatibility with the latest released version of Fleet
(see [Must
rule](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/workflows/fleetd-development-and-release-strategy.md))
- [X] Verified auto-update works from the released version of component
to the new version (see [tools/tuf/test](../tools/tuf/test/README.md))
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Chores**
* Updated the project and all included tooling modules to Go 1.26.5.
* Refreshed build images used by desktop Linux, load testing, and
related utilities to the newer Go toolchain.
* Updated change log entries to reflect the Go version bump.
* **Bug Fixes**
* Improved the automation that refreshes Go-pinned Docker image
references to resolve and apply correct digests, helping prevent broken
build images.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Lucas Manuel Rodriguez
703dcf0b4f