refactor(ui): split prompt input into hooks and API

Extract prompt draft/history, attachments, picker, and keydown logic into co-located hooks. Introduce PromptInputApi for quote/expand/setText and migrate SessionView off DOM poking; remove legacy registerQuoteHandler.

packages/ui/src/components/prompt-input/usePromptState.ts

@@ -0,0 +1,193 @@
+import { createEffect, createSignal, on, onCleanup, onMount, type Accessor } from "solid-js"
+import { addToHistory, getHistory } from "../../stores/message-history"
+import { clearSessionDraftPrompt, getSessionDraftPrompt, setSessionDraftPrompt } from "../../stores/sessions"
+import { getLogger } from "../../lib/logger"
+
+const log = getLogger("actions")
+
+type GetTextarea = () => HTMLTextAreaElement | undefined | null
+
+type PromptStateOptions = {
+  instanceId: Accessor<string>
+  sessionId: Accessor<string>
+  instanceFolder: Accessor<string>
+  onSessionDraftLoaded?: (draft: string) => void
+}
+
+type HistorySelectOptions = {
+  force?: boolean
+  isPickerOpen: boolean
+  getTextarea: GetTextarea
+}
+
+type PromptState = {
+  prompt: Accessor<string>
+  setPrompt: (value: string) => void
+  clearPrompt: () => void
+
+  draftLoadedNonce: Accessor<number>
+
+  history: Accessor<string[]>
+  historyIndex: Accessor<number>
+  historyDraft: Accessor<string | null>
+
+  resetHistoryNavigation: () => void
+  clearHistoryDraft: () => void
+  recordHistoryEntry: (entry: string) => Promise<void>
+
+  selectPreviousHistory: (options: HistorySelectOptions) => boolean
+  selectNextHistory: (options: HistorySelectOptions) => boolean
+}
+
+const HISTORY_LIMIT = 100
+
+export function usePromptState(options: PromptStateOptions): PromptState {
+  const [prompt, setPromptInternal] = createSignal("")
+  const [history, setHistory] = createSignal<string[]>([])
+  const [historyIndex, setHistoryIndex] = createSignal(-1)
+  const [historyDraft, setHistoryDraft] = createSignal<string | null>(null)
+  const [draftLoadedNonce, setDraftLoadedNonce] = createSignal(0)
+
+  const setPrompt = (value: string) => {
+    setPromptInternal(value)
+    setSessionDraftPrompt(options.instanceId(), options.sessionId(), value)
+  }
+
+  const clearPrompt = () => {
+    clearSessionDraftPrompt(options.instanceId(), options.sessionId())
+    setPromptInternal("")
+  }
+
+  const resetHistoryNavigation = () => {
+    setHistoryIndex(-1)
+    setHistoryDraft(null)
+  }
+
+  const clearHistoryDraft = () => {
+    setHistoryDraft(null)
+  }
+
+  createEffect(
+    on(
+      () => `${options.instanceId()}:${options.sessionId()}`,
+      () => {
+        const instanceId = options.instanceId()
+        const sessionId = options.sessionId()
+
+        onCleanup(() => {
+          // Persist the previous session's draft when switching sessions.
+          setSessionDraftPrompt(instanceId, sessionId, prompt())
+        })
+
+        const storedPrompt = getSessionDraftPrompt(instanceId, sessionId)
+
+        setPromptInternal(storedPrompt)
+        setSessionDraftPrompt(instanceId, sessionId, storedPrompt)
+
+        resetHistoryNavigation()
+
+        setDraftLoadedNonce((prev) => prev + 1)
+        options.onSessionDraftLoaded?.(storedPrompt)
+      },
+    ),
+  )
+
+  onMount(() => {
+    void (async () => {
+      const loaded = await getHistory(options.instanceFolder())
+      setHistory(loaded)
+    })()
+  })
+
+  const recordHistoryEntry = async (entry: string) => {
+    try {
+      await addToHistory(options.instanceFolder(), entry)
+      setHistory((prev) => {
+        const next = [entry, ...prev]
+        if (next.length > HISTORY_LIMIT) {
+          next.length = HISTORY_LIMIT
+        }
+        return next
+      })
+      setHistoryIndex(-1)
+    } catch (historyError) {
+      log.error("Failed to update prompt history:", historyError)
+    }
+  }
+
+  const canUseHistory = (selectOptions: HistorySelectOptions) => {
+    if (selectOptions.force) return true
+    if (selectOptions.isPickerOpen) return false
+
+    const textarea = selectOptions.getTextarea()
+    if (!textarea) return false
+    return textarea.selectionStart === 0 && textarea.selectionEnd === 0
+  }
+
+  const focusTextareaEnd = (getTextarea: GetTextarea) => {
+    const textarea = getTextarea()
+    if (!textarea) return
+    setTimeout(() => {
+      const next = getTextarea()
+      if (!next) return
+      const pos = next.value.length
+      next.setSelectionRange(pos, pos)
+      next.focus()
+    }, 0)
+  }
+
+  const selectPreviousHistory = (selectOptions: HistorySelectOptions) => {
+    const entries = history()
+    if (entries.length === 0) return false
+    if (!canUseHistory(selectOptions)) return false
+
+    if (historyIndex() === -1) {
+      setHistoryDraft(prompt())
+    }
+
+    const newIndex = historyIndex() === -1 ? 0 : Math.min(historyIndex() + 1, entries.length - 1)
+    setHistoryIndex(newIndex)
+    setPrompt(entries[newIndex])
+    focusTextareaEnd(selectOptions.getTextarea)
+    return true
+  }
+
+  const selectNextHistory = (selectOptions: HistorySelectOptions) => {
+    const entries = history()
+    if (entries.length === 0) return false
+    if (!canUseHistory(selectOptions)) return false
+    if (historyIndex() === -1) return false
+
+    const newIndex = historyIndex() - 1
+    if (newIndex >= 0) {
+      setHistoryIndex(newIndex)
+      setPrompt(entries[newIndex])
+    } else {
+      setHistoryIndex(-1)
+      const draft = historyDraft()
+      setPrompt(draft ?? "")
+      setHistoryDraft(null)
+    }
+    focusTextareaEnd(selectOptions.getTextarea)
+    return true
+  }
+
+  return {
+    prompt,
+    setPrompt,
+    clearPrompt,
+
+    draftLoadedNonce,
+
+    history,
+    historyIndex,
+    historyDraft,
+
+    resetHistoryNavigation,
+    clearHistoryDraft,
+    recordHistoryEntry,
+
+    selectPreviousHistory,
+    selectNextHistory,
+  }
+}