fix(agent): chat console keeps its thread across turns and reloads (#1859)

Three user-reported failures in the assistant panel, one root cause each:

1. "The chat asks what I'm referring to" when continuing a thread. The
   single-call console (general.help, AskConsole -> /api/agent/ask) was
   stateless since the 08-20 model-agnostic cutover: conversationId was only
   the tool actor id, so every turn was answered blind, reload or not.
   The provider-agnostic GenerateTextRequest gains an optional `history`
   (real message turns before the prompt, in both the Anthropic-family and
   the OpenAI-compatible adapter; absent/empty leaves the request
   byte-identical to the single-turn call). The route loads the thread's
   earlier turns server-side (loadChatHistory: text only, hidden and tool
   rows dropped, alternation repaired, newest 16 rows / 10k chars) before
   writing the new question, and hands them to the model.

2. A full page reload (the deploy prompt's "Ladda om") closed the docked
   panel and dropped the thread from view. The panel now remembers its open
   thread per tab in sessionStorage (lib/agent-panel/session-restore) and
   the provider reopens it on mount; the sheet loads it exactly like a pick
   from "Tidigare konversationer". Close and "Ny konversation" forget it; a
   thread that no longer opens is dropped instead of retried on every reload.

3. "Can't type any more" once the update banner shows. DeployReloadPrompt's
   full-width wrapper sits at z-[60] after the panel in DOM order and
   swallowed clicks on the panel's composer; only the card takes input now.


Claude-Session: https://claude.ai/code/session_01VjoXN3xdNZrHZeYA6qMi3g

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

app/api/agent/ask/route.ts

@@ -13,6 +13,7 @@ import { answerAssistantQuestion } from '@/lib/agent/ask/ask-service'
 import { EmptyModelAnswerError } from '@/lib/agent/ask/errors'
 import {
   resolveChatConversation,
+  loadChatHistory,
   persistUserTurn,
   persistAssistantTurn,
 } from '@/lib/agent/ask/persist'
@@ -152,6 +153,11 @@ export async function POST(request: Request): Promise<Response> {
     }
     const { conversationId } = resolved
 
+    // A resumed thread carries its earlier turns into the model call; read
+    // them BEFORE the new question is written so it is not sent twice. A
+    // thread created just now has nothing to load.
+    const history = resolved.created ? [] : await loadChatHistory(supabase, conversationId)
+
     await persistUserTurn(supabase, conversationId, parsed.data.question)
 
     const result = await answerAssistantQuestion({
@@ -162,6 +168,7 @@ export async function POST(request: Request): Promise<Response> {
       question: parsed.data.question,
       pageContext: parsed.data.context,
       tier: parsed.data.tier,
+      history,
     })
 
     // answerAssistantQuestion throws EmptyModelAnswerError on an empty answer,