[codex] Fix leaderboard posting

[redreceipt]

Summary

Fixes the weekly leaderboard worker path so it can post successfully and run at the intended 4pm Eastern wall-clock time.

Root cause

The completed-project contributor query declared $project_id as String!, but Linear's project.id.eq filter expects an ID. That caused a GraphQL validation error before the worker reached the Slack post.

The leaderboard schedule also used friday.at("20:00") without a timezone, unlike the other wall-clock Slack jobs. On UTC workers that resolved to 20:00 UTC instead of the intended Eastern-time schedule.

Changes

• Change the completed-project contributor query variable to ID!.
• Schedule post_leaderboard at 16:00 in America/New_York.
• Update tests to assert the query type and timezone registration.
• Stub post_inactive_engineers in the debug-job test so it stays focused on debug job orchestration.

Validation

• .venv-ci/bin/python -m unittest tests.test_jobs tests.test_linear_projects tests.test_leaderboard
• .venv-ci/bin/ruff check jobs.py tests/test_jobs.py linear/projects.py tests/test_linear_projects.py
• .venv-ci/bin/ruff format --check jobs.py tests/test_jobs.py linear/projects.py tests/test_linear_projects.py
• Verified under TZ=UTC that 16:00 America/New_York resolves to 20:00 UTC / 16:00 Eastern.