TUI: tool, resource and prompt forms still receive keys while a sampling or elicitation overlay is open #2967

Raised by Copilot's review of the v2.15.0 milestone merge (#2961), and confirmed in the source. It is a follow-up to #2829 / PR #2903.

Problem

While a sampling or elicitation request is open in PendingRequestModal, the TUI's tool, resource and prompt test modals (ToolTestModal, ResourceTestModal, PromptTestModal) gate their own useInput with inputActive={!pendingRequestOpen}, and their handleFormSubmit returns early. The ink-form <Form> each one renders in its form state is not gated, though. As the code's own comment says, "ink-form still sees its keys". Keystrokes meant for the overlay's form therefore also move focus and edit values in the form underneath it.

Impact

• Nothing is sent. Submit is blocked in all three modals.
• A draft can be silently changed. Field values and the focused field in the hidden form can change while the user answers the request.
• Narrow trigger. The form is mounted only while the modal is in its form state. A request the server sends during a call (state loading) does not leak. It happens only when a request arrives unprompted while a form is open.

Expected

While a pending request is open, the underlying form receives no input, for example by not rendering <Form> (or rendering it inert) while inputActive is false, so the draft is exactly as the user left it.