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/osiris/query.rhai

@@ -0,0 +1,21 @@
+print("Querying context [alice, bob]...");
+let ctx = get_context(["alice", "bob"]);
+print("✓ Context ID: " + ctx.context_id());
+
+print("\nListing all notes...");
+let notes = ctx.list("notes");
+print("✓ Found " + notes.len() + " note(s)");
+
+print("\nRetrieving specific note...");
+let note = ctx.get("notes", "sprint_planning_001");
+print("✓ Retrieved note: sprint_planning_001");
+
+print("\nQuerying context [alice, bob, charlie]...");
+let ctx2 = get_context(["alice", "bob", "charlie"]);
+print("✓ Context ID: " + ctx2.context_id());
+
+print("\nListing all events...");
+let events = ctx2.list("events");
+print("✓ Found " + events.len() + " event(s)");
+
+"Query complete: Found " + notes.len() + " notes and " + events.len() + " events"