feat(table): add Columns to Return to the legacy Table block's Query Rows - #9887

Summary

• The legacy Table block (table, superseded by table_v2) now has the same Columns to Return picker as table_v2. Existing workflows still run on the legacy block, and the upgrade is a Copilot-assisted rewrite rather than an automatic one.
• A query that leaves it empty behaves exactly as before. With columns selected, each returned row's data keeps only those columns, so large cells a workflow never reads no longer land in its execution data or count against the 5 MiB row-data budget.
• Wiring only, reusing the existing projection in queryTableRows:
  • table_query_rows takes an optional columns param, sent as a JSON query value.
  • The internal listTableRowsContract accepts columns, and both the GET rows route and executeTableQueryRows pass it through. The shared tableRowsQueryBaseSchema that the public v1/v2 APIs extend is unchanged.
  • The column-reference schema is extracted and shared with the v2 query body contract.
• The "Columns to Return" field, its input, and the parser (canvas selection first, a model-supplied columns as the fallback, fail fast on malformed values) now live in blocks/utils.ts, shared by both Table blocks. A malformed-JSON error now reads "Invalid JSON for Columns to Return" (was "in"), from the shared parseOptionalJsonInput.

Type of Change

• New feature (backward compatible)

Testing

• New tests, each shown red by reverting its part of the change (contract field, tool serialization, block mapping):
  • execute-tool.test.ts runs the real v1 tool serialization through the real contract decoding into the operation.
  • A legacy block transformer case in table.test.ts.
• Ran execute-tool.test.ts, table.test.ts, table_v2.test.ts, operations.test.ts, the rows route.test.ts, query_rows_v2.test.ts and blocks/utils.test.ts: 55 passed.
• Ran bun run lint, check-block-registry.ts origin/staging, check:api-validation:strict, check:explicit-any, check:client-boundary, check:tool-registry-boundary, check:utils and check:comment-hygiene. generate:tool-metadata was regenerated.
• bun run type-check (pre-push hook) passes; check:audits and the full test suite are left to CI.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing (new tests pass the test-audit authoring gate)
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)