Fix/coderabbit nits (#1259)

* fix: eliminate 8 as any in MCP handlers, structured output, and stream events

- Group A: Add : () => AnyObjectSchema type annotations to MCP notification
  schema constants (useIdeSelection, useIdeLogging, usePrompts, channelNotification)
- Group B: Add isStructuredOutputAttachmentMessage type guard for structured
  output attachment payloads (execAgentHook)
- Group C: Add isMessageDeltaStreamEvent type guard for message_delta
  stream event usage extraction (forkedAgent)

These as any casts also exist in the upstream CCB source — this fix provides
real type safety without changing any runtime behavior.

* feat: wire mode persona injection — Claude Soul Document distilled into system prompt

- prompts.ts: add getModePersonaSection() → injects current mode's
  systemPrompt as 'mode_persona' dynamic section (first in order,
  before operational instructions). Previously modes had systemPrompt
  fields but they were never sent to the model.
- modes/personas/claude.ts: 3KB distilled Claude persona from
  Anthropic's leaked Claude 4.5 Opus Soul Document (70KB → operational
  extract): core traits, 7 honesty principles, helpfulness/caution
  balance, collaboration stance, identity stability.
- With custom mode YAML (~/.claude/modes/claude.yaml), 7 modes total
  including the new Claude persona — fully operational at /mode claude.

Co-Authored-By: James Feng <47167674+GhostDragon124@users.noreply.github.com>

* fix: import path convention + reword persona source comment

- prompts.ts: use 'src/modes/store.js' alias instead of relative '../modes/store.js'
  to match the file's existing import convention
- claude.ts: reword JSDoc to say 'based on publicly available reference document'
  instead of 'leaked', addressing CodeRabbit review concern

src/utils/forkedAgent.ts

@@ -20,10 +20,14 @@ import {
 } from '../services/analytics/index.js'
 import { accumulateUsage, updateUsage } from '../services/api/claude.js'
 import { EMPTY_USAGE, type NonNullableUsage } from '@ant/model-provider'
+import type {
+  BetaRawMessageDeltaEvent,
+  BetaRawMessageStreamEvent,
+} from '@anthropic-ai/sdk/resources/beta/messages/messages.js'
 import type { ToolUseContext } from '../Tool.js'
 import type { AgentDefinition } from '@claude-code-best/builtin-tools/tools/AgentTool/loadAgentsDir.js'
 import type { AgentId } from '../types/ids.js'
-import type { Message } from '../types/message.js'
+import type { Message, StreamEvent } from '../types/message.js'
 import { createChildAbortController } from './abortController.js'
 import { logForDebugging } from './debug.js'
 import { cloneFileStateCache } from './fileStateCache.js'
@@ -492,6 +496,24 @@ export function createSubagentContext(
  * })
  * ```
  */
+
+type StreamEventMessage = StreamEvent & {
+  type: 'stream_event'
+  event: BetaRawMessageStreamEvent
+}
+
+function isMessageDeltaStreamEvent(
+  message: Message | StreamEvent,
+): message is StreamEventMessage & { event: BetaRawMessageDeltaEvent } {
+  return (
+    message.type === 'stream_event' &&
+    typeof (message as StreamEventMessage).event === 'object' &&
+    (message as StreamEventMessage).event !== null &&
+    'type' in (message as StreamEventMessage).event &&
+    (message as StreamEventMessage).event.type === 'message_delta'
+  )
+}
+
 export async function runForkedAgent({
   promptMessages,
   cacheSafeParams,
@@ -562,15 +584,8 @@ export async function runForkedAgent({
     })) {
       // Extract real usage from message_delta stream events (final usage per API call)
       if (message.type === 'stream_event') {
-        if (
-          'event' in message &&
-          (message as any).event?.type === 'message_delta' &&
-          (message as any).event.usage
-        ) {
-          const turnUsage = updateUsage(
-            { ...EMPTY_USAGE },
-            (message as any).event.usage,
-          )
+        if (isMessageDeltaStreamEvent(message)) {
+          const turnUsage = updateUsage({ ...EMPTY_USAGE }, message.event.usage)
           totalUsage = accumulateUsage(totalUsage, turnUsage)
         }
         continue