fix(tool-hints): deduplicate by formatted string + per-line inline display

Two display fixes based on real-world Feishu testing:

1. tool_hints.py: format_tool_hints now deduplicates by comparing the
   fully formatted hint string instead of tool name alone. This fixes
   `ls /Desktop` and `ls /Downloads` being incorrectly merged as
   `ls /Desktop × 2`. Truly identical calls still fold correctly.
   (_group_consecutive and all abbreviation logic preserved unchanged.)

2. feishu.py: inline tool hints now display one tool per line with
   🔧 prefix, and use double-newline trailing to prevent Setext heading
   rendering when followed by markdown `---`.

Made-with: Cursor

nanobot/channels/feishu.py

@@ -1379,7 +1379,9 @@ class FeishuChannel(BaseChannel):
                 if buf and buf.card_id:
                     if buf.tool_hint_len > 0:
                         buf.text = buf.text[:-buf.tool_hint_len]
-                    suffix = f"\n\n---\n🔧 {hint}"
+                    lines = self._format_tool_hint_lines(hint).split("\n")
+                    formatted = "\n".join(f"🔧 {ln}" for ln in lines if ln.strip())
+                    suffix = f"\n\n{formatted}\n\n"
                     buf.text += suffix
                     buf.tool_hint_len = len(suffix)
                     buf.sequence += 1