feat(brand): pen-nib logo + the nib glyph across the TUI

Adopt the fountain-pen-nib logo (from the docs site) as the canonical mark: assets/logo-light.png + logo-dark.png, shown at the top of the README via <picture> (light/dark). In the TUI, the prompt and section/status markers now use the brand nib glyph (the pen-nib motif) instead of the per-theme fleuron; the theme palette still follows the active theme (test updated to match).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: vikast908

README.md

@@ -1,5 +1,10 @@
 <div align="center">
 
+<picture>
+  <source media="(prefers-color-scheme: dark)" srcset="assets/logo-dark.png">
+  <img src="assets/logo-light.png" alt="Writing Agent" width="128">
+</picture>
+
 <img src="assets/writing-agent-banner.svg" alt="Writing Agent - a self-correcting, autonomous writing system that turns a topic into a publication-ready manuscript" width="820">
 
 ### an autonomous writing studio - books, articles & more

assets/logo-dark.png

@@ -38,12 +38,13 @@ def _sync_palette() -> None:
     for k in ("GOLD", "GOLD_HI", "INK", "PARCH", "DIM", "RULE", "ERR",
               "ON_CLR", "OFF_CLR"):
         g[k] = getattr(ui, k)
-    g["_FLEURON"] = ui.FLEURON
+    g["_FLEURON"] = _NIB
 _NODES = ["planner", "toc", "writer", "critic", "judge", "verifier", "summarizer",
           "consolidation", "production", "learner", "researcher", "humanizer",
           "diagram", "diagram_fallback", "chat"]
 _EXIT = {"exit", "quit", "q", ":q"}
-_FLEURON = ui.FLEURON
+_NIB = "✒"             # the brand glyph: a pen nib (matches the logo)
+_FLEURON = _NIB            # used for the prompt + section/status markers
 _MAX_HISTORY = 10  # max messages kept for multi-turn context (5 user + 5 assistant)
 
 _SLASH_HELP = [
@@ -2054,7 +2055,7 @@ def run_shell(parser, commands, cfg: ModelConfig, settings: Settings) -> None:
                     pass
             elif global_mode == "article":
                 sfx_plain = " [article]"  # no active book - show global mode
-            prompt_plain = f"\n❧ {slug}{book_part}{sfx_plain} "
+            prompt_plain = f"\n{_NIB} {slug}{book_part}{sfx_plain} "
         elif console:
             mode_tag = f" [{INK}]article[/]" if not book and global_mode == "article" else ""
             prompt_plain = (f"\n[{GOLD}]{_FLEURON}[/] "

assets/logo-light.png

@@ -43,7 +43,8 @@ def test_shell_sync_palette_follows_theme():
     ui.apply_theme("violet-bloom")
     shell._sync_palette()
     assert shell.GOLD == ui.THEMES["violet-bloom"]["GOLD"]
-    assert shell._FLEURON == ui.THEMES["violet-bloom"]["FLEURON"]
+    # The prompt/marker glyph is the fixed brand nib (matches the logo), not the per-theme fleuron.
+    assert shell._FLEURON == shell._NIB == "✒"
 
 
 def test_themes_are_visually_distinct():