test: cover emission allocation edge cases

[CaptainTimon]

Summary

• Add reference allocation coverage for the Convert per-repo weight from unbounded multiplier to emission_share (bounded pool slice) #1215 emission rules
• Cover fixed per-repo caps, within-repo PR/issue split, side spill, empty-repo recycle, and registry slack recycle
• Add a high-volume repo case proving a busy repo remains capped at its configured slice

Related Issues

Part of #1215. Covers required deliverable 6 only.

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (describe below)

Test coverage for the allocation/recycle/spill behavior.

Testing

• Tests added/updated
• Manually tested

uv run pytest tests/validator/test_emission_allocation_coverage.py -q
uv run ruff check gittensor/validator/emission_allocation.py tests/validator/test_emission_allocation_coverage.py
uv run ruff format --check gittensor/validator/emission_allocation.py tests/validator/test_emission_allocation_coverage.py
uv run pytest -q

Checklist

• Code follows project style guidelines
• Self-review completed
• Changes are documented (if applicable)

Note for reviewers: this PR intentionally adds reference coverage. The separate #1215 implementation PRs provide the config and allocation primitives that these cases pin down.

[CaptainTimon]

@anderdc in my opinion this method is the most elegant, optimal, clear and safe.
could you please review my PR and give me feedback?
thanks.

[anderdc]

Fold these changes into a single PR addressing #1215, not 11 slices. Closing.