Tax reports: working workbook and agent tools

The excel format of the Modelo 303, 347 and 130 was a published contract that always failed: announced in the enum, in the request schemas, in the v1 route and in the CLI's --format excel, and returning 422 unsupported_format in every case. It now produces a real workbook. See Tax reports.

• format: "excel" works for the three models — POST /v1/tax_reports/303, /347 and /130 return a .xlsx workbook with two sheets, Resumen and Detalle, both headed by model, fiscal period and declaring company. Amounts are written as numbers, so a column can be summed in the sheet; zeros are written as 0 rather than left blank.
• 347 — summary of declared clients and suppliers, total amount and how many counterparties cleared the 3,005.06 € threshold; one detail row per counterparty with its NIF, province, annual base and four quarters, which add up to the base. 303 — the aggregates that determine the balance, with accrued VAT and surcharge broken down by tax rate. 130 — derived boxes in the summary, starting boxes in the detail.
• It is not filed with the AEAT, and it says so inside the file — the first rows of Resumen carry the notice that the workbook is working material and that filing happens with the official TXT. Its figures are still trustworthy: they come from the same domain calculation as the official file, so two formats of the same filing can never disagree.
• A year with no counterparty above the threshold still produces a workbook, with an empty detail sheet and a summary that says so. It is the ordinary case for a small company, not an error.
• Nine new MCP tools for a domain that had nine published routes and no tools: generate_tax_report_303, generate_tax_report_347 and generate_tax_report_130 (tax_reports:write), plus preview, find-by-period, history, stats, activities and download (tax_reports:read). No new scope family — both scopes already existed. See the tool catalog.