fix pr265 chapter diagrams

Author: Gui-Yue

s02_tool_use/README.en.md

@@ -170,6 +170,8 @@ The teaching version's separation is clearer for teaching — readers immediatel
 
 ### 2. Concurrency Safety: isConcurrencySafe()
 
+![Tool Concurrency](images/concurrency-comparison.en.svg)
+
 The teaching version executes tools one by one in original order, without concurrency. CC uses `isConcurrencySafe(input)` to determine concurrency — note this isn't simply "read-only vs write", but judges by specific input:
 
 | | isReadOnly | isConcurrencySafe |

s02_tool_use/README.ja.md

@@ -170,6 +170,8 @@ Agent は 5 つの専用ツールを持つようになった。file tools は `s
 
 ### 二、並列安全性：isConcurrencySafe()
 
+![Tool Concurrency](images/concurrency-comparison.ja.svg)
+
 教育版は元の順序で一つずつ実行し、並列処理は行わない。CC は `isConcurrencySafe(input)` で並列可否を判断する — これは単なる「読み取り専用 vs 書き込み」ではなく、具体的な入力で判断する：
 
 | | isReadOnly | isConcurrencySafe |

s02_tool_use/README.md

@@ -170,6 +170,8 @@ s03 Permission → 在工具执行之前加一道门：这个操作安全吗？
 
 ### 二、并发安全判断：isConcurrencySafe()
 
+![Tool Concurrency](images/concurrency-comparison.svg)
+
 教学版按原始顺序逐个执行，不做并发。CC 用 `isConcurrencySafe(input)` 判断能否并发——注意这不是简单的"只读 vs 写"，而是按具体输入判断：
 
 | | isReadOnly | isConcurrencySafe |