fix: use default-foreground ANSI so splash and spinner stay readable in light-mode terminals

Bright-white (\033[97m) and plain-white (\033[37m) collapse to invisible
on terminals where the foreground IS white — the user reports 'Team
License' and 'Syncing CodeGraph' rendering blank on a light-mode iTerm
profile. Same problem with Rich's 'bold white' style.

Fix: switch every body-text white to \033[39m (default foreground) and
'bold white' to plain 'bold' in the installer. Default foreground inherits
the terminal's theme so text shows black on light, white on dark, and
stays readable on both.

Add launcher/tests/unit/test_ansi_safety.py to ban \033[97m, \033[37m,
'bold white', '[white]', and '[dim white]' from launcher/ + installer/
sources so the regression cannot reappear. The single legitimate
white-on-red 'Pilot disabled' banner is allowlisted explicitly.

Author: maxritter

installer/ui.py

@@ -135,7 +135,7 @@ def banner(self, license_info: dict[str, Any] | None = None) -> None:
 
         tagline = Text()
         tagline.append("  ✈ ", style="cyan")
-        tagline.append("How real engineers run Claude Code.", style="bold white")
+        tagline.append("How real engineers run Claude Code.", style="bold")
         self._console.print(tagline)
         self._console.print("    From requirement to production-grade code. Planned, tested, verified.", style="muted")
         self._console.print()
@@ -184,7 +184,7 @@ def step(self, name: str) -> None:
             return
         step_text = Text()
         step_text.append(f"[{self._current_step}/{self._total_steps}] ", style="bold magenta")
-        step_text.append(name, style="bold white")
+        step_text.append(name, style="bold")
         self._console.print()
         self._console.print(Rule(step_text, style="magenta"))
 
@@ -231,7 +231,7 @@ def next_steps(self, sections: list[tuple[str, list[tuple[str, str]]]]) -> None:
         step_num = 1
         for section_title, items in sections:
             self._console.print()
-            self._console.print(f"  [bold white]{section_title}[/bold white]")
+            self._console.print(f"  [bold]{section_title}[/bold]")
             self._console.print()
             for title, description in items:
                 self._console.print(f"  [bold magenta]{step_num}.[/bold magenta] [bold]{title}[/bold]")