feat: support Agent Window sizing (session start --width/--height, window resize) (#52)

- `bsk session start --width <px> --height <px>` opens the Agent Window
  with the given outer size (chrome.windows.create)
- new `bsk window resize --session <id> --width <px> --height <px>`
  resizes the Agent Window at runtime (chrome.windows.update)
- both validated on CLI, daemon and extension sides (100..=7680 CSS px)
- protocol: new tool.window_resize method (BrowserMutation) and
  optional width/height on tool.session_start params; schemas regenerated

crates/bsk-cli/src/cli/mod.rs

@@ -30,6 +30,7 @@ pub mod status;
 pub mod tab;
 pub mod update;
 pub mod waits;
+pub mod window;
 
 use clap::{Args, Parser, Subcommand};
 
@@ -50,6 +51,7 @@ use crate::cli::snapshot::SnapshotArgs;
 use crate::cli::tab::TabCmd;
 use crate::cli::update::UpdateArgs;
 use crate::cli::waits::{WaitForNavigationArgs, WaitMsArgs};
+use crate::cli::window::WindowCmd;
 
 /// Tool calls wait slightly longer than the daemon's 30s tool timeout so
 /// callers receive the structured daemon timeout instead of dropping the
@@ -118,6 +120,9 @@ pub enum Command {
     /// Tab management commands.
     Tab(TabCmd),
 
+    /// Agent Window management commands.
+    Window(WindowCmd),
+
     /// Capture a PNG of the active tab or a snapshot ref element.
     Screenshot(ScreenshotArgs),