fix(github): preserve status channel identity

[Kewe63]

Fixes #98

Functional change

GithubStatusMonitor.wait_for_statuses previously flattened commit statuses and check runs into a single map keyed only by display name. If both GitHub API channels reported a check with the same name, the check run overwrote the commit status and the expected checks were deduplicated.

A failed commit status named build could therefore be hidden by a successful check run named build, causing the monitor to report success after observing only one effective check.

This change preserves the GitHub API channel as part of each check's identity. A same-named commit status and check run are now tracked independently, and a failure in either channel prevents success.

Behavior and output

• The public checks and check_runs inputs remain unchanged.
• Every requested item in both channels must reach a successful terminal state.
• Same-named checks no longer overwrite or deduplicate each other.
• Progress, timeout, and failure output uses channel-qualified labels such as status: build and check run: build.
• Legacy string keys remain supported by the internal watcher and rendering helpers.

Implementation

• Introduce a channel-qualified Check identity.
• Preserve that identity while polling statuses and check runs.
• Carry the identity through watcher state, transitions, errors, and rendering.
• Add public wait_for_statuses regressions covering same-named failures and successful checks in both channels.

Verification

• PYTHONPATH=github/src pytest -q github/tests — 55 passed after merging current main
• ruff check github/src github/tests — passed
• ruff format --check github/src github/tests — passed

[danielgafni]

Sorry I was mass-closing PRs!

Please rewrite the PR description to address the functional change.

[Kewe63]

Updated the PR description to explicitly document the functional change and preserved behavior. I also merged the latest main; all CI checks are passing now.