Add cluv submit command for SLURM job submission

[lebrice]

Summary

• Adds `cluv submit <job.sh> [sbatch-flags...] [-- program-args...]` — a clean replacement for the manual `safe_sbatch` pattern.
• Enforces a clean git state, syncs the project, injects `GIT_COMMIT`, then runs `sbatch` on the remote with configurable `SBATCH_*` env vars.
• Job script is a required positional argument — not configurable via `pyproject.toml`.
• Arguments before `--` are forwarded as sbatch flags; arguments after `--` are passed to the job script.
• Extends `[tool.cluv]` config with global SLURM defaults (`[tool.cluv.slurm]`) and per-cluster overrides (`[tool.cluv.clusters.]`).
• Migrates `clusters = [...]` list to `[tool.cluv.clusters.*]` sub-tables; old list format still works for backward compat.

Config shape:

[tool.cluv.slurm]
SBATCH_TIME = "3:00:00"

[tool.cluv.clusters.mila]
SBATCH_PARTITION = "long"

[tool.cluv.clusters.rorqual]
SBATCH_ACCOUNT = "def-bengioy"
SBATCH_PARTITION = "main"

Usage:

cluv submit rorqual scripts/job.sh
cluv submit rorqual scripts/job.sh --partition=gpu --mem=40G
cluv submit rorqual scripts/job.sh --partition=gpu -- python train.py --lr=0.001

Test plan

• `uv run pytest tests/test_config.py tests/test_submit.py -v` — all unit tests pass
• `uv run pytest -m integration -v` — `test_submit_rorqual_builds_correct_command` passes with an active rorqual connection
• `uv run cluv submit --help` — verify help output shows new positional syntax
• `uv run cluv status` — verify cluster list still loads correctly from new config format

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.71770% with 103 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.78%. Comparing base (73fa4c4) to head (4412a59).

Files with missing lines	Patch %	Lines
cluv/cli/submit.py	28.57%	30 Missing ⚠️
cluv/remote.py	67.77%	29 Missing ⚠️
cluv/cli/sync.py	32.25%	21 Missing ⚠️
cluv/__main__.py	0.00%	16 Missing ⚠️
cluv/cli/login.py	57.14%	3 Missing ⚠️
cluv/cli/status.py	40.00%	3 Missing ⚠️
cluv/cli/run.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #10      +/-   ##
==========================================
+ Coverage   40.00%   40.78%   +0.78%     
==========================================
  Files          11       13       +2     
  Lines         725      868     +143     
==========================================
+ Hits          290      354      +64     
- Misses        435      514      +79     

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