Remove flock mode (superseded by studio)

Flock mode has been superseded by the studio multi-agent workspace manager.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

@@ -1356,7 +1356,6 @@ dependencies = [
  "g3-computer-control",
  "g3-config",
  "g3-core",
- "g3-ensembles",
  "g3-planner",
  "g3-providers",
  "hex",
@@ -1461,23 +1460,6 @@ dependencies = [
  "walkdir",
 ]
 
-[[package]]
-name = "g3-ensembles"
-version = "0.1.0"
-dependencies = [
- "anyhow",
- "chrono",
- "clap",
- "g3-config",
- "g3-core",
- "serde",
- "serde_json",
- "tempfile",
- "tokio",
- "tracing",
- "uuid",
-]
-
 [[package]]
 name = "g3-execution"
 version = "0.1.0"