Consent-dialog tool rendering rebuilt around refusing stubs

The old helpers that pre-rendered a tool-use line for the consent dialog, including a try/catch fallback that reported render errors, were removed. In their place, unknown or remote tools now get a stub tool descriptor, and both the stub and its preview renderer throw rather than render when asked to display anything unbounded: more than three parameters, over-long keys or values, or oversized arrays and objects. In practice, a permission prompt for a tool this process does not have will show just the tool name instead of a rendering of its arguments.