fix: align appended emissions records to existing CSV headers

[nawaaaaaAaar]

Fixes #1442.

Align append records with the existing CSV's header order before writing a headerless row. has_valid_headers already allows reordered headers, but the append path previously wrote values in dataclass order, corrupting their column associations.

Only the existing header is read, not historical rows. New-file and update-mode behavior is unchanged; all-None columns remain present.

Verification on Python 3.12.13:

• Real CSV regression fails in append mode before the fix; update-mode control passes.
• Package test command: 681 passed, two skipped, three integration cases deselected, twelve subtests passed.
• All applicable autoflake/isort/Black/flake8 hooks passed.

The regression verifies every field in the appended row with csv.DictReader, including identifiers, emissions, energy, and coordinates. Concurrent CSV writers, remote filesystems, visualization and API/dashboard integration were not tested.

AI disclosure: autonomously reproduced, implemented, and tested using Perplexity Computer (GPT-6.1). No human review is claimed.

Combined with #1439 and #1441: 695 passed, two skipped, three integration cases deselected and twelve subtests passed. PR is open and ready for review; hosted verification workflows require maintainer approval. A successful PR-size labeler is not a hosted test pass.

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[davidberenstein1957]

Good fix for #1442: reindexing the appended row to the file's header is safe because has_valid_headers already guarantees the same column set, and the test uses a real CSV. One ordering note for the maintainers: #1419 touches the same file for a problem master has already fixed, so it should be closed before this one merges, otherwise it would conflict.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.07%. Comparing base (7929a4f) to head (4458cbf).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1443   +/-   ##
=======================================
  Coverage   92.07%   92.07%           
=======================================
  Files          49       49           
  Lines        5199     5202    +3     
=======================================
+ Hits         4787     4790    +3     
  Misses        412      412           

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[benoit-cty]

Thanks,

The test is good: it compares every field of the appended row through csv.DictReader and uses update mode as a control.

I've done small changes: The CSV header is now read once and used both for the check and for reordering the appended row:

• New helper _read_headers() returns the file's header row, or None if the file is empty.
• has_valid_headers(data, headers=None) takes the header row as an optional argument and reads the file itself only when none is passed.
• out() reads the header once, passes it to has_valid_headers, and reuses it for reindex(). That removes the second file open the PR had added.