[VisLab]

• The 11 ECMAScript # members in src/ become _x with a JSDoc @Private tag, matching hed-typescript's private _x. No behavior change.
• BidsHedTsvParser._braceRegEx gets a JSDoc block.
• datasetParser.spec.js reads BidsFileAccessor._SUFFIXES.length instead of a hardcoded 7, as hed-typescript does.
• ESLint no-restricted-syntax rejects PrivateIdentifier (#x).
• copilot-instructions.md states the convention.

Addresses #946.

[Copilot]

🟢 Approval recommended

No active review issues are blocking approval of the private-member naming changes.

No open issues 🎉

What changed in this PR

Aligns private-member naming in hed-javascript with hed-typescript for issue #946, using underscore-prefixed members and JSDoc annotations instead of ECMAScript private syntax.

Changes:

• Converts 11 # members to underscore-prefixed members with @private annotations and updates their references.
• Adds an ESLint restriction against # members and documents the convention.
• Updates the dataset parser test to derive its expected category count from _SUFFIXES.

File	Description
tests/​otherTests/​datasetParser.spec.js	Derives the expected count from _SUFFIXES.length.
src/​utils/​paths.js	Renames the path-organization state field.
src/​schema/​specs.js	Renames the schema specification backing map.
src/​schema/​entries/​tag.js	Renames the cached ancestor field.
src/​parser/​reservedChecker.js	Renames the singleton instance field.
src/​parser/​parsedHedTag.js	Renames the normalized-tag field.
src/​parser/​parsedHedGroup.js	Renames the normalized-group cache.
src/​bids/​validator/​tsvValidator.js	Renames private methods and the regex field; documents the regex.
src/​bids/​types/​file.js	Renames the validator-class backing field.
src/​bids/​datasetParser.js	Renames the static suffix list.
eslint.config.mjs	Rejects ECMAScript private identifiers.
.github/​copilot-instructions.md	Documents underscore naming and @private annotations.

_{Review effort: Balanced}