Remove flock mode (superseded by studio)

Flock mode has been superseded by the studio multi-agent workspace manager.

Changes:
- Remove g3-ensembles crate entirely
- Remove --project, --flock-workspace, --segments, --flock-max-turns CLI flags
- Remove run_flock_mode() from autonomous.rs
- Remove flock-related tests from cli_integration_test.rs
- Update README.md, docs/architecture.md, analysis/memory.md
- Delete docs/FLOCK_MODE.md

Cargo.toml

@@ -7,7 +7,6 @@ members = [
     "crates/g3-config",
     "crates/g3-execution",
     "crates/g3-computer-control",
-    "crates/g3-ensembles",
     "crates/studio"
 ]
 resolver = "2"