Create core_eia176__yearly_gas_supply

[MeadBarrel]

Overview

Closes #4711 .

What problem does this address?

EIA Form 176 Part 4 (Lines 1.0-7.0) contains operator-level natural and
supplemental gas supply data, including production, storage withdrawals, receipts,
supplemental gaseous fuels, and reported total supply for the report state. This
data was available in the extracted EIA-176 inputs but was not yet exposed as a
PUDL core table.

This table exposes the source-reported Part 4 summary fields. It does not include
the granular continuation-line details for Line 3.0 receipts or Line 6.0
supplemental gaseous fuels.

What did you change?

• Added core_eia176__yearly_gas_supply with one row per
  (operator_id_eia, report_year).
• Included standardized Mcf fields for natural gas production, synthetic gas
  production, storage withdrawals, state or U.S. border receipts, citygate
  receipts, other receipts, supplemental gaseous fuels, and reported total
  supply.
• Added transform validation comparing reported Line 7.0 total supply against
  the sum of reported component fields, with a bounded allowance for known
  historical source-data inconsistencies.
• Added continuation-line validation for Line 3.0 receipts and Line 6.0
  supplemental gaseous fuels.
• Added table and field metadata for the new output table, including notes about
  continuation-line detail and historical total-supply inconsistencies.
• Added an Alembic migration for the new table.
• Added dbt row-count and non-negative value expectations.

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Documentation

Make sure to update relevant aspects of the documentation:

• Update the release notes: reference the PR and related issues.
• Update relevant Data Source jinja templates (see docs/data_sources/templates).
• Update relevant table or source description metadata (see src/metadata).
• Review and update any other aspects of the documentation that might be affected by this PR.

Testing

How did you make sure this worked? How can a reviewer verify this?

To-do list

• If updating analyses or data processing functions: make sure to update row count expectations in dbt tests.
• Run pixi run prek-run to run linters and static code analysis checks.
• Run pixi run pytest-ci locally to ensure that the merge queue will accept your PR.
• Review the PR yourself and call out any questions or issues you have.
• For PRs that change the PUDL outputs significantly, run the full ETL locally and then run the data validations using dbt. If you can't run the ETL locally then run the build-deploy-pudl GitHub Action manually and ensure that it succeeds.

[e-belfer]

I think we can make this into a nice skinny table by stacking all the columns into a volume_mcf and a categorical supply_type column. That'll require redoing the migration and dropping these new field definitions for the most part. total_supply_mcf can be streamlined to just total.

It looks like total citygate gets split into two components after 2010. No action item here, but we should note it in the table description.

Looking at the log scale, everything else seems pretty reasonable, with above ground withdrawals being understandably somewhat spiky over time.

[e-belfer]

Once #5219 merges, we'll need to update the alembic migrations to refer to the new head. Otherwise this is ready to go!

Edit: #5219 was bounced from the queue, so merging this first.