feat(tooling): replace tox with just

[fselmo]

🗒️ Description

Continues from #635 and:

• fixes merge conflicts
• cleans up tox (we don't need to keep this around)
• cleans up unused default group
• adds descriptions to the justfile so that just --list has these
• clarifies just fill -> just fill-ci. This just command hides away --clean and uses full parallelism (-n=auto) which could be really heavy for users and destructive (removes old fixtures). I think we should keep using uv run fill for full control and this just command should just be for CI ease. Marked it private... this can be expanded later if desired.
• cleans up the references across skills and files

🔗 Related Issues or PRs

• supersedes feat(tooling): replace tox with just #635

✅ Checklist

• Ran just checks to avoid unnecessary CI fails:

  just check

• Considered adding appropriate tests for the changes.
• Considered updating the online docs in the ./docs/ directory.

[fselmo]

Hey @tcoratger. This PR just fixes the conflicts that exist on #635 and adds a cleanup commit on top, removing tox altogether, adding descriptions to just recipes, and cleaning a few things up. Looks good from my end, if you want to add a sanity check here and merge 👀.

[fselmo]

Hmm is this a flaky test?

> [0](https://github.com/leanEthereum/leanSpec/actions/runs/25391087107/job/74465464690?pr=709#step:6:401)
----------------------------------------------------------------------------------------------------------------
TOTAL                                                                10734    749   2456    245    92%
Coverage HTML written to dir htmlcov
Required test coverage of 90.0% reached. Total coverage: 91.51%
============================= slowest 10 durations =============================
52.45s call     tests/lean_spec/subspecs/xmss/test_aggregation.py::test_aggregate_three_children
46.34s call     tests/lean_spec/forks/lstar/forkchoice/test_validator.py::TestBlockProduction::test_produce_block_with_attestations
37.65s call     tests/lean_spec/subspecs/xmss/test_aggregation.py::test_aggregate_children_of_children
22.70s call     tests/lean_spec/subspecs/networking/test_reqresp.py::TestBoundaryConditions::test_payload_at_max_size
19.50s call     tests/lean_spec/subspecs/networking/service/test_service.py::TestAggregatedAttestationDispatch::test_gossip_aggregated_attestation_routed
16.47s call     tests/lean_spec/forks/lstar/state/test_state_aggregation.py::test_build_block_state_root_valid_when_signatures_split
11.55s call     tests/lean_spec/forks/lstar/forkchoice/test_attestation_target.py::TestSafeTargetAdvancement::test_safe_target_requires_supermajority
10.14s call     tests/lean_spec/subspecs/networking/test_reqresp.py::TestBoundaryConditions::test_response_payload_at_max_size
10.04s call     tests/lean_spec/subspecs/node/test_node.py::TestNodeShutdown::test_wait_shutdown_stops_network_service
10.04s call     tests/lean_spec/subspecs/node/test_node.py::TestNodeShutdown::test_wait_shutdown_stops_chain_service
=========================== short test summary info ============================
FAILED tests/lean_spec/subspecs/networking/gossipsub/integration/test_mesh_formation.py::test_mesh_forms_within_d_parameters - AssertionError: peerK: mesh size 1 outside [2, 5]
assert 2 <= 1
 +  where 2 = GossipsubParameters(protocol_id='/meshsub/1.2.0', d=3, d_low=2, d_high=5, d_lazy=2, heartbeat_interval_secs=999.0, fanout_ttl_secs=5, mcache_len=6, mcache_gossip=3, seen_ttl_secs=120).d_low
=========== 1 failed, 3290 passed, 59 warnings in 166.94s (0:02:46) ============
error: Recipe `test` failed on line 66 with exit code 1

Will look into it but should be unrelated to the changes here

---

edit: re-running failed CI now to see if it passes

[fselmo]

Hmm is this a flaky test?
...
Will look into it but should be unrelated to the changes here

edit: re-running failed CI now to see if it passes

Ok, re-ran and it passed. Without much context, may be worth a look for flakiness.

[tcoratger]

Thanks a lot!