Remove flock mode (superseded by studio)

Flock mode has been superseded by the studio multi-agent workspace manager.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/src/cli_args.rs

@@ -79,22 +79,6 @@ pub struct Cli {
     #[arg(long)]
     pub safari: bool,
 
-    /// Enable flock mode - parallel multi-agent development
-    #[arg(long, requires = "flock_workspace", requires = "segments")]
-    pub project: Option<PathBuf>,
-
-    /// Flock workspace directory (where segment copies will be created)
-    #[arg(long, requires = "project")]
-    pub flock_workspace: Option<PathBuf>,
-
-    /// Number of segments to partition work into (for flock mode)
-    #[arg(long, requires = "project")]
-    pub segments: Option<usize>,
-
-    /// Maximum turns per segment in flock mode (default: 5)
-    #[arg(long, default_value = "5")]
-    pub flock_max_turns: usize,
-
     /// Enable planning mode for requirements-driven development
     #[arg(long, conflicts_with_all = ["autonomous", "auto", "chat"])]
     pub planning: bool,