fix(serialization): render concept labels in XBRL/JSON-LD export

[jfrench9]

Summary

Fundamental concepts (Assets, Cash, Liabilities, Revenues, Goodwill, …) rendered as their QName (rs-gaap:Assets) instead of their label in the XBRL export (arelle) and the JSON-LD skos:prefLabel. Root cause: the serialization bundle sourced the concept label from element.description (NULL for these) rather than the standard label linkbase, and the QName-echo suppression then dropped the element.name fallback for single-word concepts whose name equals the QName localpart. This sources the standard label instead, and backfills standard labels for 5 concepts that genuinely had none.

Changes

Serialization — operations/serialization/bundle.py

• BundleElement.label is now sourced from element_labels (role=standard, lang=en), falling back to element.description only when no standard label exists. Adds a scoped ElementLabel query in build_report_bundle and a standard_label param on _element_to_bundle.
• Fixes the 9 affected single-word fundamentals (Assets, Cash, Communication, Depletion, Depreciation, Goodwill, Land, Liabilities, Revenues) in both the XBRL label linkbase and JSON-LD skos:prefLabel (jsonld.py emits prefLabel from BundleElement.label), and broadly improves prefLabel coverage (previously the near-always-null description).
• 3 regression tests: standard label overrides description; sourced when name == localname; a single-word label equal to the localname is emitted in the label linkbase.

Taxonomy data — frameworks/rs-gaap/packages/rs-gaap/v1/taxonomy.jsonld

• Added rdfs:label (the standard label) to 5 previously-unlabeled concepts: IncomeTaxExpenseBenefitContinuingOperations, LiabilitiesAndPartnersCapital, NetInterestIncomeLossAfterProvisionForLoanLosses, SecondaryProcessingRevenue, VehicleTollRevenue. All 5 are tenant-excluded verticals, so this affects only the public library / full-taxonomy export (the library-browser view where they showed as QNames); it needs a library reseed to land.

Testing

• uv run pytest tests/operations/serialization/ → 125 passed (incl. the 3 new).
• ruff check / ruff format / basedpyright on changed files → clean.
• Verified the data path: rs-gaap:Assets has element_labels role=standard text="Assets" in the seeded library, so the new query sources it.
• Not regenerated an actual arelle export this session; the 5 added labels require just reset-local to reach the public library. just test-all not run.

Notes / Follow-ups

• Tenant exports were already covered by the serialization fix (the 9 fundamentals have standard labels seeded); the 5 JSON-LD additions only affect the public / full-taxonomy export.
• _concept_label's name == localname suppression is retained as a final fallback for concepts with neither a standard label nor a description (acceptable — truly unlabeled → QName).