feat: EditorRuntimeActor - 三层缓存/delta/事件架构

Phase A — EditorRuntimeActor 内存缓存层
- 新增 editor_actor.rs: EditorBlockDocument 内存态 + apply_command + load_or_init
- block.rs 四个写工具（replace/insert/delete/move）接入 actor 路径
- editor_actor feature flag（MNOTE_WEB_ENABLE_EDITOR_ACTOR=true 默认开启）
- bridge-runtime 三个核心函数公开化
- rust-toolchain: 1.89 → stable（修复 spike WASM 编译阻塞）

Phase B — 编辑器增量 delta channel
- BlockDelta/DeltaOperation 类型 + actor.build_block_delta()
- leptos-tiptap spike: mnote:editor:block-delta CustomEvent 监听 + JSON patch
- DocumentAiAgentPanel: 拦截 blockDelta → window dispatchEvent
- 工具响应含 blockDelta 字段供前端消费

Phase C — 事件 stream delta
- broadcast channel 在 AppState/actor/SSE 三层贯通
- tree_events SSE 端点发 block.delta 事件
- 旧客户端降级兼容

环境修复
- rustc recursion_limit = 1024（修复 Leptos SSR 类型深度溢出）
- run-convex-deploy.js（封装 Convex function 部署到本地后端 3210）

ref: design/07-ai/process/7-13-page-block-editor-runtime-actor-v1.md

rust/crates/mnote-web/src/page_aggregate/builder.rs

@@ -13,6 +13,7 @@ use crate::page_aggregate::{
     PageAggregate, PageAggregateSource, PageBody, PageHead, PageIdentity, PageLayout, PageOptions,
     PagePermissions, PageStats, PageTree,
 };
+use bridge_runtime::project_legacy_content_to_block_document;
 use serde_json::{to_value, Value};
 
 /// PageAggregate 构建器。
@@ -284,6 +285,13 @@ impl PageAggregateBuilder {
 
     /// 消费 builder 并产出 `PageAggregate`。
     pub fn build(self) -> PageAggregate {
+        let block_document = project_legacy_content_to_block_document(
+            &self.document_id,
+            &self.content,
+            &self.revision,
+        )
+        .ok();
+        let block_projection_version = if block_document.is_some() { 1 } else { 0 };
         let page_options = PageOptions {
             wide_layout: self.wide_layout,
             small_text: self.small_text,
@@ -336,6 +344,9 @@ impl PageAggregateBuilder {
                 content: self.content,
                 revision: self.revision,
                 conflict_detection_key: self.conflict_detection_key,
+                block_document: block_document.unwrap_or(Value::Null),
+                block_projection_version,
+                projection_source: "builder.content".into(),
             },
             tree: PageTree {
                 page_subtree: self.page_subtree,