Chore: register the unmute_click pytest marker (Part 2/2)

[AmaadMartin]

Please ensure you have read the contribution guide before creating a pull request.

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):
   Closes: #issue_number
   Related: #issue_number
2. Or, if no issue exists, describe the change:

Problem: tests/unittests/cli/utils/test_cli_tools_click.py applies
@pytest.mark.unmute_click nine times (L1640, L1696, L1732, L1766, L1800,
L1837, L1867, L1911, L1949), and its autouse _mute_click fixture reads it at
L83-L86 to let a test opt out of the click.echo mute. The marker is registered
nowhere, so every run of that file emits nine warnings:

PytestUnknownMarkWarning: Unknown pytest.mark.unmute_click - is this a typo?
You can register custom marks to avoid this warning

Solution: Register the marker in the existing [tool.pytest] table in
pyproject.toml, keeping the dotted ini_options.* key style already used
there. This is the canonical one-key fix — no conftest.py pytest_configure
hook, no new file.

No other marker in the repo is registered, so this introduces the markers key
for the first time; it is purely additive. It does not enable
--strict-markers, so it cannot make a previously-passing test fail — the only
observable effect is pytest's warning output.

Key placement (after ini_options.testpaths, before the asyncio_* keys) is
what pyproject-fmt 2.24.0 — the version pinned in .pre-commit-config.yaml —
requires; pyproject-fmt --check pyproject.toml reports no change.

Stacking: this is part 2 of 2, based on
fix/telemetry-cli-no-subcommand-exit-code-assertion (#51), which fixes a stale
exit-code assertion in the same test file. The two were split on review because
they are independent concerns: the nine marker usages and the _mute_click
fixture both pre-date either branch (added in 6bab08fc), so this registration
stands on its own. It is stacked rather than parallel only so its CI reflects a
tree where the sibling failure is already fixed.

Collision check: ran gh pr list --state open --limit 100 on this fork (48
open PRs) and diffed the file lists of every plausibly adjacent one. Three
(#17, #25, #31) touch pyproject.toml, but their hunks are dependency additions
and a [tool.codespell] table — none registers pytest markers or touches
[tool.pytest]. No collision.

Testing Plan

Please describe the tests that you ran to verify your changes. This is required for all PRs that are not small documentation or typo fixes.

Unit Tests:
[x] I have added or updated unit tests for my change.
[x] All unit tests pass locally.

This is a pytest configuration change and adds no production line, so it has no
new code to cover. It is verified by the existing suite plus a direct check that
the warning is gone.

Run locally on the exact pushed commit (Python 3.13, uv sync --extra test ->
click==8.4.2):

pytest tests/unittests/cli/utils/test_cli_tools_click.py -q        # 52 passed
pytest tests/unittests/cli -q                                      # 564 passed, 5 skipped
pytest tests/unittests/cli/utils/test_cli_tools_click.py -q 2>&1 \
  | grep -c PytestUnknownMarkWarning                               # 0  (was 9)

Proving the change is load-bearing. Making the warning an error turns the
registration into a pass/fail gate, and the branch was run both with and without
the hunk:

pytest tests/unittests/cli/utils/test_cli_tools_click.py -q \
  -W "error::pytest.PytestUnknownMarkWarning"

Tree	Result
with the ini_options.markers hunk	52 passed
hunk reverted (git stash push pyproject.toml)	ERROR ... pytest.PytestUnknownMarkWarning / Interrupted: 1 error during collection

Lint checks run locally against the changed file, at the pinned
.pre-commit-config.yaml versions:

pyproject-fmt==2.24.0 --check pyproject.toml   # no change for pyproject.toml
codespell==2.4.2 pyproject.toml                # clean

Manual End-to-End (E2E) Tests:
Please provide instructions on how to manually test your changes, including any necessary setup or configuration.

uv sync --extra test
# Before this change: nine PytestUnknownMarkWarning lines.
# After: zero, and the marked tests still opt out of the click mute.
pytest tests/unittests/cli/utils/test_cli_tools_click.py -q 2>&1 \
  | grep -c PytestUnknownMarkWarning

The marker still functions — test_telemetry_first_run_prompt_opt_in and its
siblings assert on prompt text that is only visible because _mute_click
honours the marker and skips the click.echo patch. Those assertions pass, so
registration did not change the marker's behaviour.

Expected CI status: absent, validated locally instead. The workflow triggers
on pull_request: branches: [main, v1]
(.github/workflows/continuous-integration.yml:25-31), and this PR's base is
fix/telemetry-cli-no-subcommand-exit-code-assertion, so no test job will run.
The commands and results recorded above were run on the exact pushed commit.

For reference, the Pre-commit Linter job also fails on this fork for a
pre-existing, unrelated reason — the update-constraints hook errors with
Resolution failed even without constraints on every PR, including ones that
touch no pyproject.toml (e.g. #45).

Checklist

[x] I have read the CONTRIBUTING.md document.
[x] I have performed a self-review of my own code.
[x] I have commented my code, particularly in hard-to-understand areas.
[x] I have added tests that prove my fix is effective or that my feature works.
[x] New and existing unit tests pass locally with my changes.