#9350 fix(workflows): accept legacy input field types instead of rejecting them

Summary

• Follow-up to #9342 so it is strictly non-regressive. Stored Start inputs carry a long tail of types outside the editor's list (json, legacy widget names like short-input, textarea, select). Before the shared run schema started throwing on them, they ran with the executor passing values through unchanged.
• Run validation / MCP schema: an unknown type now accepts any value and advertises no type, instead of a 400. Manual, copilot, and MCP runs and deploy-time MCP schema sync work again for these workflows. Reserved input names still return 400.
• Save path: restores the pre-#9342 array-only input-format check, so edits to workflows carrying legacy types are not rejected and rows are stored unchanged.
• Executor: reverts the json coercion alias, so deployed runs behave exactly as before. json is treated like any other legacy type on every side; files stays an alias of file[], which both sides already apply.

Type of Change

• Bug fix

Testing

• Targeted vitest: input-schema, editing/validation, start-block, run-options, mcp/workflow-tool-schema, input-format, mcp workflow lifecycle (172 passed).
• Red/green: the 4 new/changed cases fail against the current staging source and pass with this change.
• bun run lint, check:unused-exports, check:comment-hygiene, check:test-patterns, check:client-boundary, check:boundaries, check:utils, check:source-conventions.
• Full suite, type-check, and audits run in 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)