Remove flock mode (superseded by studio)

Flock mode has been superseded by the studio multi-agent workspace manager.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

crates/g3-cli/Cargo.toml

@@ -11,7 +11,6 @@ g3-planner = { path = "../g3-planner" }
 g3-computer-control = { path = "../g3-computer-control" }
 g3-providers = { path = "../g3-providers" }
 clap = { workspace = true }
-g3-ensembles = { path = "../g3-ensembles" }
 tokio = { workspace = true }
 anyhow = { workspace = true }
 tracing = { workspace = true }