fix(metadata,cli): drop unnamed columns so R-exported CSVs validate (#109)

[Mandyx22]

What

Fixes finding #2 of #109: a real jsPsych dataset exported from R fails Psych-DS validation because of an unnamed row-index column.

R's write.csv (with the default row.names = TRUE) prepends an unnamed row-index column, so the CSV header starts with a bare comma — an empty-string column name. Psych-DS variables require a name, so the column can never appear in variableMeasured. Previously:

• the library skipped it, logging Name field is missing. Variable not added. once per row, and
• the CLI copied the CSV verbatim,

leaving a column in the file with no metadata entry and failing validation with CSV_COLUMN_MISSING_FROM_METADATA.

How

The library owns variableMeasured; the CLI owns the on-disk CSV — so both must agree, or the file the validator reads won't match the metadata.

• stripUnnamedColumns(rows) — new exported helper in the metadata package that drops empty/whitespace-only-named columns in place and reports which were dropped.
• generate() strips unnamed columns from the parsed data up front, with a single warning instead of per-row spam.
• CLI writer re-serialises a .csv input that contains unnamed columns (column order preserved) so the written file matches variableMeasured; well-formed CSVs are still copied byte-for-byte. Mirrored on the JSON→CSV conversion path too.

Chose to drop the column (the issue's suggested option a) rather than synthesize a name — it's a meaningless row index, so dropping yields the least-surprising valid dataset.

Testing

• 3 new library tests + 4 new CLI tests; full suite green (299 tests).
• End-to-end: ran the built CLI against a synthetic R-style dataset — the written header went from ,subject_id,trial_type,… to subject_id,trial_type,… and CSV_COLUMN_MISSING_FROM_METADATA no longer appears. (The lone residual time_elapsed error is finding Incorporating Psych-DS validator with the metadata module #1, addressed separately on fix(metadata): register jsPsych system variables lazily (#109) #110; this branch is off main.)

🤖 Generated with Claude Code

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🦋 Changeset detected

Latest commit: 57b5bcf

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@jspsych/metadata	Patch
@jspsych/metadata-cli	Patch
frontend	Patch

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[Mandyx22]

Superseded by #114 — finding #2 is re-cut on top of #103's shared buildPsychDSDataFiles so the CLI and frontend share one data-shaping path. The library stripUnnamedColumns + generate() strip here carry over; the CLI verbatim-write rewrite is replaced by the strip inside the shared builder. Closing to avoid review on the old shape.