Adopt session.redirect (issue #710) (#714)

* Add session.redirect affordance (issue #710)

Route send through session.redirect while a turn is streaming and the prompt
is plain text (no attachments, not a /command); otherwise prompt.submit.
Adds WsMethods.SESSION_REDIRECT + HermesWsClient.sendRedirect. No separate
button — the composer already sends mid-turn, so send just does the redirect.

* fix(chat): capture typing state before sendMessage for redirect

Capture wasStreaming state before updating uiState.isAgentTyping so normal sends call prompt.submit.

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/test/java/com/m57/hermescontrol/ui/chat/ChatViewModelTest.kt

@@ -1117,6 +1117,23 @@ class ChatViewModelTest {
             verify { HermesWsClient.sendMessage(sessionId, "Hello Hermes", any()) }
         }
 
+    @Test
+    fun testSendMessageRedirectWhenStreaming() =
+        runTest {
+            val (viewModel, sessionId) = createViewModelWithSession()
+
+            // First send starts streaming
+            viewModel.sendMessage("Hello Hermes")
+            advanceUntilIdle()
+            assertTrue(viewModel.uiState.value.isAgentTyping)
+
+            // Second send while streaming triggers redirect
+            viewModel.sendMessage("Wait, correction")
+            advanceUntilIdle()
+
+            verify { HermesWsClient.sendRedirect(sessionId, "Wait, correction", any()) }
+        }
+
     // ── Session switch ───────────────────────────────────────────────────────
 
     @Test