Add yamlfmt to task fmt

[mmatczuk]

No description provided.

[claude]

Non-reproducible dependency: @latest means every invocation can install a different version of yamlfmt, which can cause inconsistent formatting across developers and CI. The existing install-golangci-lint task pins to a specific version via a variable and uses sources for caching.

Pin yamlfmt to a specific version (e.g., @v0.16.0) using a variable (like GOLANGCI_LINT_VERSION), and add a sources block so the task is cached and only re-runs when the version changes.

[josephwoodward]

As Claude suggests, would it be better to pin it to a specific version for consistency?

[mmatczuk]

My take is that it's the legacy of the future, who would bump it and why?

[claude]

Commits
LGTM

Review
The PR adds yamlfmt as a YAML formatting tool to the task fmt pipeline. One issue found with dependency management.

1. Non-reproducible dependency (taskfiles/tools.yml#L31): install-yamlfmt uses @latest instead of a pinned version, unlike the existing install-golangci-lint pattern which pins via a version variable and uses sources for caching. This can cause inconsistent formatting across environments.