feat(terminal): tint terminal background per agent color

Add backend-agnostic terminal color support via OSC escape sequences:
- New backend/terminal.py with palette_printf() and exec_shell_script()
  shared by both Docker and smolmachines bottle backends
- Emits OSC 4 (indexed palette) + OSC 11 (default background tint)
  before launching; resets both on agent exit via OSC 104/111
- OSC 11 background tint is visible even when the TUI uses true/24-bit
  colors (which bypass the palette), as Codex does for its chrome
- Fix Codex [tui] config: status_line=["model-with-reasoning"],
  theme="ansi" (dark-ansi and cwd/directory were invalid identifiers)

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

tests/unit/test_agent_provider.py

@@ -80,7 +80,7 @@ class TestAgentProviderRuntime(unittest.TestCase):
         self.assertTrue(plan.has_prompt)
         self.assertEqual("Existing instructions.\n", prompt)
         self.assertIn("[tui]", config)
-        self.assertIn('status_line = ["model", "cwd"]', config)
+        self.assertIn('status_line = ["model-with-reasoning"]', config)
         self.assertIn('terminal_title = ["spinner", "project"]', config)
 
     def test_codex_forward_host_credentials_adds_auth_and_verify(self):

tests/unit/test_backend_terminal.py

@@ -0,0 +1,83 @@
+"""Unit tests for backend/terminal.py palette and shell-script helpers."""
+
+from __future__ import annotations
+
+import unittest
+
+from bot_bottle.backend.terminal import exec_shell_script, palette_printf
+
+
+class TestPalettePrintf(unittest.TestCase):
+    def test_known_color_returns_printf(self):
+        cmd = palette_printf("red")
+        self.assertTrue(cmd.startswith("printf '"))
+        self.assertIn("\\033]4;1;", cmd)   # normal red
+        self.assertIn("\\033]4;9;", cmd)   # bright red
+        self.assertIn("\\033]11;", cmd)    # default background tint
+
+    def test_bright_variant_sets_both_slots(self):
+        cmd = palette_printf("bright-blue")
+        self.assertIn("\\033]4;12;", cmd)  # bright-blue
+        self.assertIn("\\033]4;4;", cmd)   # blue
+
+    def test_unknown_color_returns_empty(self):
+        self.assertEqual("", palette_printf(""))
+        self.assertEqual("", palette_printf("neon-pink"))
+
+    def test_all_named_colors_produce_output(self):
+        colors = [
+            "black", "red", "green", "yellow",
+            "blue", "magenta", "cyan", "white",
+            "bright-black", "bright-red", "bright-green", "bright-yellow",
+            "bright-blue", "bright-magenta", "bright-cyan", "bright-white",
+        ]
+        for color in colors:
+            with self.subTest(color=color):
+                self.assertTrue(palette_printf(color))
+
+
+class TestExecShellScript(unittest.TestCase):
+    _ARGV = ["smolvm", "machine", "exec", "--name", "x", "--", "claude"]
+
+    def test_no_decoration_returns_none(self):
+        self.assertIsNone(exec_shell_script(self._ARGV))
+        self.assertIsNone(exec_shell_script(self._ARGV, terminal_title="", terminal_color=""))
+
+    def test_title_only_uses_exec(self):
+        script = exec_shell_script(self._ARGV, terminal_title="my-agent")
+        assert script is not None
+        self.assertIn("printf", script)
+        self.assertIn("my-agent", script)
+        self.assertIn("exec ", script)
+        # No palette reset when there's no color
+        self.assertNotIn("\\033]104", script)
+
+    def test_color_only_sets_palette_and_resets(self):
+        script = exec_shell_script(self._ARGV, terminal_color="green")
+        assert script is not None
+        self.assertIn("\\033]4;", script)   # indexed palette
+        self.assertIn("\\033]11;", script)  # background tint
+        self.assertIn("\\033]104", script)  # palette reset
+        self.assertIn("\\033]111", script)  # background reset
+        # No exec-replace when palette is active (shell must survive for reset)
+        parts = script.split("; ")
+        agent_part = next(p for p in parts if "smolvm" in p)
+        self.assertFalse(agent_part.startswith("exec "))
+
+    def test_title_and_color_both_appear(self):
+        script = exec_shell_script(self._ARGV, terminal_title="bot", terminal_color="cyan")
+        assert script is not None
+        self.assertIn("bot", script)
+        self.assertIn("\\033]4;", script)
+        self.assertIn("\\033]11;", script)
+        self.assertIn("\\033]104", script)
+        self.assertIn("\\033]111", script)
+
+    def test_title_with_special_chars_is_quoted(self):
+        script = exec_shell_script(self._ARGV, terminal_title="my agent's label")
+        assert script is not None
+        self.assertNotIn("my agent's label", script)  # must be shell-quoted
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/unit/test_contrib_codex_provider.py

@@ -165,9 +165,9 @@ class TestCodexProvisionPrompt(unittest.TestCase):
         self.assertTrue(plan.has_prompt)
         self.assertEqual("Existing instructions.\n", prompt_text)
         self.assertIn("[tui]", config)
-        self.assertIn('status_line = ["model", "cwd"]', config)
+        self.assertIn('status_line = ["model-with-reasoning"]', config)
         self.assertIn('terminal_title = ["spinner", "project"]', config)
-        self.assertIn('theme = "dark-ansi"', config)
+        self.assertIn('theme = "ansi"', config)
 
 
 class TestCodexProvisionSkills(unittest.TestCase):