fix(ci): preserve JSON structure of changes output in build-matrix step

[Copilot]

fromJson in the test-installation strategy matrix fails on PRs that only modify a subset of packages because the dorny/paths-filter changes output (e.g., ["kerncap","metrix"]) is interpolated inside a double-quoted echo, causing the shell to strip the inner quotes and write invalid JSON ([kerncap,metrix]) to GITHUB_OUTPUT.

Change

Assign the expression to a shell variable using single quotes before echoing — the same pattern already used for ALL:

- echo "packages=${{ steps.filter.outputs.changes }}" >> "$GITHUB_OUTPUT"
+ CHANGES='${{ steps.filter.outputs.changes }}'
+ echo "packages=${CHANGES}" >> "$GITHUB_OUTPUT"

GHA expands ${{ }} before the shell runs, so the shell sees CHANGES='["kerncap","metrix"]'; single quotes preserve the JSON intact.

[Copilot]

Pull request overview

This PR adjusts the CI workflow’s “Build package matrix” step so the dorny/paths-filter changes output remains valid JSON when written to GITHUB_OUTPUT, preventing fromJson(...) from failing when only a subset of packages changes.

Changes:

• Store ${{ steps.filter.outputs.changes }} in a single-quoted shell variable before emitting it as a job output.
• Update the packages output emission to use the intermediate CHANGES variable, preserving JSON quoting.

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[coleramos425]

Looks good. This PR fixed the reoccuring failures observed in the Intellikit CI Test job, e.g.