Add persistent workspace shell sessions

Let agents inhabit a workspace across separate calls instead of only submitting one-shot execs.

Add workspace shell open/read/write/signal/close across the CLI, Python SDK, and MCP server, with persisted shell records, a local PTY-backed mock implementation, and guest-agent support for real Firecracker workspaces.

Mark the 2.5.0 roadmap milestone done, refresh docs/examples and the release metadata, and verify with uv lock, UV_CACHE_DIR=.uv-cache make check, and UV_CACHE_DIR=.uv-cache make dist-check.

examples/python_shell.py

@@ -0,0 +1,34 @@
+from __future__ import annotations
+
+import tempfile
+import time
+from pathlib import Path
+
+from pyro_mcp import Pyro
+
+
+def main() -> None:
+    pyro = Pyro()
+    with tempfile.TemporaryDirectory(prefix="pyro-workspace-seed-") as seed_dir:
+        Path(seed_dir, "note.txt").write_text("hello from shell\n", encoding="utf-8")
+        created = pyro.create_workspace(environment="debian:12", seed_path=seed_dir)
+        workspace_id = str(created["workspace_id"])
+        try:
+            opened = pyro.open_shell(workspace_id)
+            shell_id = str(opened["shell_id"])
+            pyro.write_shell(workspace_id, shell_id, input="pwd")
+            deadline = time.time() + 5
+            while True:
+                read = pyro.read_shell(workspace_id, shell_id, cursor=0)
+                output = str(read["output"])
+                if "/workspace" in output or time.time() >= deadline:
+                    print(output, end="")
+                    break
+                time.sleep(0.1)
+            pyro.close_shell(workspace_id, shell_id)
+        finally:
+            pyro.delete_workspace(workspace_id)
+
+
+if __name__ == "__main__":
+    main()