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/process/which.rhai

@@ -0,0 +1,25 @@
+print("Checking if a command exists in the system PATH using which()...\n");
+
+// Check for a command that likely exists (e.g., 'node' or 'git')
+let command_name_exists = "node";
+let command_path_exists = which(command_name_exists);
+
+if (command_path_exists != "") {
+    print(`'${command_name_exists}' executable found at: ${command_path_exists}`);
+} else {
+    print(`'${command_name_exists}' executable not found in PATH.`);
+}
+
+print("\nChecking for a command that likely does NOT exist...");
+
+// Check for a command that likely does not exist
+let command_name_nonexistent = "nonexistent_command_abc_123";
+let command_path_nonexistent = which(command_name_nonexistent);
+
+if (command_path_nonexistent != "") {
+    print(`'${command_name_nonexistent}' executable found at: ${command_path_nonexistent}`);
+} else {
+    print(`'${command_name_nonexistent}' executable not found in PATH.`);
+}
+
+print("\nwhich() example finished.");