feat: add roomba shell (iRobot Roomba j7+ vacuum emulator)

New novelty shell emulating RoombaOS with cleaning, scheduling,
diagnostics, floor map, and humorous history entries. Bump version
to 0.16.0.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

oubliette.toml.example

@@ -34,6 +34,11 @@ password = "admin"
 # password = "cisco"
 # shell = "cisco"
 
+# [[auth.static_credentials]]
+# username = "irobot"
+# password = "roomba"
+# shell = "roomba"
+
 [storage]
 db_path = "oubliette.db"
 retention_days = 90
@@ -75,6 +80,9 @@ hostname = "ubuntu-server"
 # db_name = "postgres"
 # pg_version = "15.4"
 
+# [shell.roomba]
+# No configuration options currently.
+
 # [detection]
 # enabled = true
 # threshold = 0.6          # 0.0–1.0, sessions above this trigger notifications