feat: add request-scoped context policies (#2914)

* feat: add request-scoped context policies

Add named turn profiles under agents.defaults so callers can opt into
per-request context and tool policies without changing default chat behavior.

Profiles can disable history, system context, skill prompts, or tools, and can
limit skills/tools with allow lists. Wire profile selection through Pico message
payloads, agent turn execution, Web chat selection, and Web visual config.

Reject invalid turn profiles before saving config through Web APIs and document
the new request context policy behavior.

* fix: address turn profile review blockers

* feat: simplify request context policy config

* fix: suppress tool prompt when turn tools are disabled

* fix: enforce turn profile tool restrictions

web/frontend/src/components/chat/chat-composer.tsx

@@ -1,5 +1,5 @@
 import { IconArrowUp, IconPhotoPlus, IconX } from "@tabler/icons-react"
-import type { KeyboardEvent } from "react"
+import { useRef, type KeyboardEvent as ReactKeyboardEvent } from "react"
 import { useTranslation } from "react-i18next"
 import TextareaAutosize from "react-textarea-autosize"
 
@@ -52,14 +52,25 @@ export function ChatComposer({
 }: ChatComposerProps) {
   const { t } = useTranslation()
   const canInput = inputDisabledReason === null
+  const composingRef = useRef(false)
   const disabledMessage =
     inputDisabledReason === null
       ? null
       : t(`chat.disabledPlaceholder.${inputDisabledReason}`)
   const placeholder = disabledMessage ?? t("chat.placeholder")
 
-  const handleKeyDown = (e: KeyboardEvent<HTMLTextAreaElement>) => {
-    if (e.nativeEvent.isComposing) return
+  const handleKeyDown = (e: ReactKeyboardEvent<HTMLTextAreaElement>) => {
+    const nativeEvent = e.nativeEvent as Event & {
+      isComposing?: boolean
+      keyCode?: number
+    }
+    if (
+      composingRef.current ||
+      nativeEvent.isComposing ||
+      nativeEvent.keyCode === 229
+    ) {
+      return
+    }
     if (e.key === "Enter" && !e.shiftKey) {
       e.preventDefault()
       onSend()
@@ -98,6 +109,12 @@ export function ChatComposer({
         <TextareaAutosize
           value={input}
           onChange={(e) => onInputChange(e.target.value)}
+          onCompositionStart={() => {
+            composingRef.current = true
+          }}
+          onCompositionEnd={() => {
+            composingRef.current = false
+          }}
           onKeyDown={handleKeyDown}
           placeholder={placeholder}
           disabled={!canInput}

web/frontend/src/components/chat/chat-page.tsx

@@ -351,7 +351,7 @@ export function ChatPage() {
       <div
         ref={scrollRef}
         onScroll={handleScroll}
-        className="min-h-0 flex-1 overflow-y-auto px-4 py-6 [scrollbar-gutter:stable] md:px-8 lg:px-24 xl:px-48"
+        className="min-h-0 flex-1 [scrollbar-gutter:stable] overflow-y-auto px-4 py-6 md:px-8 lg:px-24 xl:px-48"
       >
         <div className="mx-auto flex w-full max-w-250 flex-col gap-8 pb-8">
           {messages.length === 0 && !isTyping && (