[ENH] BEP032: Remove the channel_label column

[bendichter]

Implements the decision we reached in the working group meeting on 2026-07-29 about channel_label, addressing #2307 (comment) and following up on #2307 (comment). This targets bep032-review, so it merges into #2307 rather than into master.

The Change

channel_label is removed from channels.tsv. The column was defined as a human readable identifier for specifying the content of signals not generated by electrodes, but a channel already has an identifier in the required name column, and the categories its examples gave are values of the type column. This BEP added SYNC and BEH to that enum, and SYSCLOCK, TRIG, STIM, and MISC were there already.

Anything the type column does not capture belongs in description, so rather than deleting the column and leaving nothing in its place, this adds a description addendum to channels.tsv pointing at that use:

For a channel that is not generated by an electrode, and so has n/a in the electrode_name column, use this column to state what the signal is, for example, Synchronization pulse from the behavioral control system. The category of such a channel is given by the type column, for example, SYNC or BEH.

The example phrasing there is deliberate. @lzehl made the point in the meeting that behavioral signals and behavioral cues, the examples the removed column carried, are terms rather than descriptions, so the addendum shows a description that actually describes something.

Scope

This is a small change. channel_label appeared only in objects/columns.yaml and the microephysChannels rule, and was not used in any example table or referenced in any prose, so nothing else needed updating.

Verification

bidsschematools tests pass (81 passed, 1 skipped), as do pre-commit on the changed files and npm run remark. I confirmed no references to channel_label remain anywhere in src/, and that the rendered channels table now carries the addendum on description.

@lzehl, this is the fourth item from the meeting. The others are #2480, #2481, and #2482.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.09%. Comparing base (3f661db) to head (8140e5c).

Additional details and impacted files

@@              Coverage Diff               @@
##           bep032-review    #2483   +/-   ##
==============================================
  Coverage          83.09%   83.09%           
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  Files                 22       22           
  Lines               1698     1698           
==============================================
  Hits                1411     1411           
  Misses               287      287           

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