When the developer extension gets a cancellation message, it should kill any running processes that it owns. (#4604)

Cargo.lock

@@ -2824,6 +2824,7 @@ dependencies = [
  "indoc",
  "keyring",
  "lazy_static",
+ "libc",
  "lopdf",
  "lru",
  "mcp-core",
@@ -2848,6 +2849,7 @@ dependencies = [
  "thiserror 1.0.69",
  "tokio",
  "tokio-stream",
+ "tokio-util",
  "tracing",
  "tracing-appender",
  "tracing-subscriber",
@@ -6790,9 +6792,9 @@ dependencies = [
 
 [[package]]
 name = "tokio-util"
-version = "0.7.15"
+version = "0.7.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "66a539a9ad6d5d281510d5bd368c973d636c02dbf8a67300bfb6b950696ad7df"
+checksum = "14307c986784f72ef81c89db7d9e28d6ac26d16213b109ea501696195e6e3ce5"
 dependencies = [
  "bytes",
  "futures-core",