fix(web): validate the edited replay draft, not just its seed

Copilot's fifth pass: one comment, and the completion of the previous round's
fix. Seeding the editor from `replayableParams` stopped it *offering* a key
the dispatcher would drop, but nothing stopped one being typed in — adding
`_meta` to a `tools/list` draft still let Send close the modal and discard it.

`parseParamsDraft` now takes the method and rejects any key the dispatch would
not read, so Send is disabled with the offending names rather than silently
dropping them. It asks the same `replayableParams` the seed is built from, so
the editor and the dispatcher cannot disagree about which keys survive.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UL9retfvAXRgvi6EWk4SY4
Signed-off-by: cliffhall <cliff@futurescale.com>

clients/web/src/components/groups/EditReplayModal/EditReplayModal.test.tsx

@@ -136,6 +136,48 @@ describe("EditReplayModal", () => {
     ).toBeInTheDocument();
   });
 
+  // Seeding from the projection is only half of it: a key the dispatcher does
+  // not read can be *added* to the draft, and Send would then discard an edit
+  // the user was looking at.
+  it("disables Send for a key this method's dispatch would not read", async () => {
+    renderWithMantine(
+      <EditReplayModal {...baseProps} method="tools/list" params={undefined} />,
+    );
+    await setAceText('{"cursor":"abc","_meta":{"progressToken":1}}');
+    expect(screen.getByRole("button", { name: "Send" })).toBeDisabled();
+    expect(
+      screen.getByText(/`_meta` is not carried by tools\/list/),
+    ).toBeInTheDocument();
+  });
+
+  it("re-enables Send once the unsupported key is removed", async () => {
+    renderWithMantine(
+      <EditReplayModal {...baseProps} method="tools/list" params={undefined} />,
+    );
+    await setAceText('{"cursor":"abc","_meta":{}}');
+    expect(screen.getByRole("button", { name: "Send" })).toBeDisabled();
+
+    await setAceText('{"cursor":"abc"}');
+    expect(screen.getByRole("button", { name: "Send" })).not.toBeDisabled();
+    expect(screen.queryByText(/not carried by/)).toBeNull();
+  });
+
+  // The check is per method, not a fixed key list: `arguments` is read by a
+  // tool call and by nothing on a list request.
+  it("judges a key against the method it would be sent to", async () => {
+    const { rerender } = renderWithMantine(
+      <EditReplayModal {...baseProps} method="tools/call" />,
+    );
+    await setAceText('{"name":"echo","arguments":{"a":1}}');
+    expect(screen.getByRole("button", { name: "Send" })).not.toBeDisabled();
+
+    rerender(<EditReplayModal {...baseProps} method="tools/list" />);
+    expect(screen.getByRole("button", { name: "Send" })).toBeDisabled();
+    expect(
+      screen.getByText(/`name`, `arguments` are not carried by tools\/list/),
+    ).toBeInTheDocument();
+  });
+
   it("closes without sending when cancelled", async () => {
     const user = userEvent.setup();
     const onSend = vi.fn();