chore: update devsper configuration and logging enhancements

- Rename .hivemind directory to .devsper in .gitignore.
- Update devsper.toml to change planner and worker models to "github:copilot".
- Enhance logging in agent.py to capture task failure details.
- Modify controller.py to include previous task outputs in payload for workers.
- Clean up unused imports and improve comments in various files.
- Update examples and documentation to reflect changes in worker model and usage instructions.

Author: rithulkamesh

.gitignore

@@ -24,7 +24,7 @@ env/
 registry/.env
 
 # Hivemind runtime and output
-.hivemind/
+.devsper/
 .events/
 
 # Example outputs (generated)
@@ -49,5 +49,6 @@ tmp
 
 node_modules
 
-# Rust (worker crate)
+# Rust (workspace and worker crate)
+target/
 worker/target/