feat: reorganize examples and add signature support to JobBuilder

- Reorganized examples into osiris/, sal/, and utils/ folders
- Moved hardcoded scripts to separate .rhai files
- Added signature() method to JobBuilder for job signing
- Updated OSIRIS context to use block_in_place instead of runtime
- Removed runtime field from OsirisContext
- Added typed save() methods for Note and Event objects
- Updated all examples to use new structure and APIs

examples/sal/scripts/mycelium/mycelium_send_message.rhai

@@ -0,0 +1,25 @@
+// Script to send a Mycelium message
+
+// API URL for Mycelium
+let api_url = "http://localhost:1111";
+
+// Send a message
+// TO SEND A MESSAGE FILL IN THE DESTINATION IP ADDRESS
+// -----------------------------------------------------//
+print("\nSending a message:");
+let destination = "50e:6d75:4568:366e:f75:2ac3:bbb1:3fdd"; // IMPORTANT: Replace with the actual destination IP address
+let topic = "test_topic";
+let message = "Hello from Rhai sender!";
+let deadline_secs = -10; // Seconds we wait for a reply
+
+try {
+    print(`Attempting to send message to ${destination} on topic '${topic}'`);
+    let result = mycelium_send_message(api_url, destination, topic, message, deadline_secs);
+    print(`result: ${result}`);
+    print(`Message sent: ${result.success}`);
+    if result.id != "" {
+        print(`Message ID: ${result.id}`);
+    }
+} catch(err) {
+    print(`Error sending message: ${err}`);
+}