feat(cli): make stream renderer use bot_name and bot_icon (#3650)

Threads bot_name/bot_icon through ThinkingSpinner and StreamRenderer
with safe defaults that preserve current behavior.

- ThinkingSpinner uses bot_name in its status text
- StreamRenderer header is "<icon> <name>" when icon is set,
  or just "<name>" when icon is empty
- Removes the now-unused __logo__ import (the cat emoji is the
  default value of bot_icon, not a hardcoded constant)

nanobot/cli/stream.py

@@ -14,8 +14,6 @@ from rich.live import Live
 from rich.markdown import Markdown
 from rich.text import Text
 
-from nanobot import __logo__
-
 
 def _make_console() -> Console:
     """Create a Console that emits plain text when stdout is not a TTY.
@@ -32,11 +30,11 @@ def _make_console() -> Console:
 
 
 class ThinkingSpinner:
-    """Spinner that shows 'nanobot is thinking...' with pause support."""
+    """Spinner that shows '<bot_name> is thinking...' with pause support."""
 
-    def __init__(self, console: Console | None = None):
+    def __init__(self, console: Console | None = None, bot_name: str = "nanobot"):
         c = console or _make_console()
-        self._spinner = c.status("[dim]nanobot is thinking...[/dim]", spinner="dots")
+        self._spinner = c.status(f"[dim]{bot_name} is thinking...[/dim]", spinner="dots")
         self._active = False
 
     def __enter__(self):
@@ -76,9 +74,17 @@ class StreamRenderer:
       on_end -> Live stops (content stays on screen)
     """
 
-    def __init__(self, render_markdown: bool = True, show_spinner: bool = True):
+    def __init__(
+        self,
+        render_markdown: bool = True,
+        show_spinner: bool = True,
+        bot_name: str = "nanobot",
+        bot_icon: str = "🐈",
+    ):
         self._md = render_markdown
         self._show_spinner = show_spinner
+        self._bot_name = bot_name
+        self._bot_icon = bot_icon
         self._buf = ""
         self._live: Live | None = None
         self._t = 0.0
@@ -91,7 +97,7 @@ class StreamRenderer:
 
     def _start_spinner(self) -> None:
         if self._show_spinner:
-            self._spinner = ThinkingSpinner()
+            self._spinner = ThinkingSpinner(bot_name=self._bot_name)
             self._spinner.__enter__()
 
     def _stop_spinner(self) -> None:
@@ -108,7 +114,8 @@ class StreamRenderer:
             self._stop_spinner()
             c = _make_console()
             c.print()
-            c.print(f"[cyan]{__logo__} nanobot[/cyan]")
+            header = f"{self._bot_icon} {self._bot_name}" if self._bot_icon else self._bot_name
+            c.print(f"[cyan]{header}[/cyan]")
             self._live = Live(self._render(), console=c, auto_refresh=False)
             self._live.start()
         now = time.monotonic()