chore(ci): run the test matrix on uipath- runners

[tibrnui]

What

Moves the test matrix onto the uipath- runner pool:

• os: [ubuntu-latest, windows-latest] -> os: [uipath-ubuntu-latest, uipath-windows-latest]
• runs-on goes back to ${{ matrix.os }} (the label-mapping expression is no longer needed)

After this, every job in the repo runs on the centralized managed pool.

Heads-up: required status checks

GitHub builds a matrix job's check-run name from the matrix values, so this renames
the test contexts, e.g.

test / Test (3.11, ubuntu-latest) -> test / Test (3.11, uipath-ubuntu-latest)

The branch ruleset still requires the stock names, so those contexts will sit as
"Expected - waiting for status to be reported" and this PR (and every later PR)
will stay BLOCKED until a repo admin updates the required status checks to the
uipath- names.

🤖 Generated with Claude Code