Fix rank-0 coord select guard and fbe doc typo

[d-chambers]

Description

Two small fixes surfaced by a CodeRabbit review while integrating master into dev (#769). Split out here so the integration merge stays a pure merge.

• dascore/core/coords.py — _select_by_sample_array guarded on ndim > 1, so a rank-0 coord (e.g. CoordPartial(shape=())) slipped past and then crashed on np.arange(len(self)) with an opaque TypeError. Changed to ndim != 1, matching the sibling guards already used in align_to, get_sample_count, and change_length. Added a regression test.
• dascore/transform/fbe.py — fixed the "orginal" typo and the unbalanced parenthesis in the dB docstring formula (20 * log10( sqrt(mean(x^2)) )).

A third finding (map_fiber _set_scale scale validation) was intentionally left alone — it's a private helper in an obscure plotting path where bad input already errors, and hardening it wasn't worth the added code.

Checklist

I have (if applicable):

• referenced the GitHub issue this PR closes.
• documented the new feature with docstrings and/or appropriate doc page. (docstring corrected)
• included tests. (rank-0 select regression test)
• added the "ready_for_review" tag once the PR is ready to be reviewed.

Verification

• pytest tests/test_core/test_coords.py::TestDimensionalityErrors tests/test_transform/test_fbe.py — passed.
• pre-commit run --files <changed> — passed.

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: f9c633de-5f0d-422e-aa5b-a2b01a91b9a5

📥 Commits

Reviewing files that changed from the base of the PR and between 09aac2f and 5de0332.

📒 Files selected for processing (3)

• dascore/core/coords.py
• dascore/transform/fbe.py
• tests/test_core/test_coords.py

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-scale-and-1d-guards

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.93%. Comparing base (09aac2f) to head (5de0332).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #771   +/-   ##
=======================================
  Coverage   99.93%   99.93%           
=======================================
  Files         145      145           
  Lines       12859    12859           
=======================================
  Hits        12851    12851           
  Misses          8        8           

Flag	Coverage Δ
unittests	99.93% <100.00%> (ø)

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