feat(display): configurable tool preview length -- show full paths by default (#3841)

Tool call previews (paths, commands, queries) were hardcoded to truncate
at 35-40 chars across CLI spinners, completion lines, and gateway progress
messages. Users could not see full file paths in tool output.

New config option: display.tool_preview_length (default 0 = no limit).
Set a positive number to truncate at that length.

Changes:
- display.py: module-level _tool_preview_max_len with getter/setter;
  build_tool_preview() and get_cute_tool_message() _trunc/_path respect it
- cli.py: reads config at startup, spinner widget respects config
- gateway/run.py: reads config per-message, progress callback respects config
- run_agent.py: removed redundant 30-char quiet-mode spinner truncation
- config.py: added display.tool_preview_length to DEFAULT_CONFIG

Reported by kriskaminski

cli.py

@@ -449,6 +449,14 @@ try:
 except Exception:
     pass  # Skin engine is optional — default skin used if unavailable
 
+# Initialize tool preview length from config
+try:
+    from agent.display import set_tool_preview_max_len
+    _tpl = CLI_CONFIG.get("display", {}).get("tool_preview_length", 0)
+    set_tool_preview_max_len(int(_tpl) if _tpl else 0)
+except Exception:
+    pass
+
 # Neuter AsyncHttpxClientWrapper.__del__ before any AsyncOpenAI clients are
 # created.  The SDK's __del__ schedules aclose() on asyncio.get_running_loop()
 # which, during CLI idle time, finds prompt_toolkit's event loop and tries to
@@ -4782,8 +4790,10 @@ class HermesCLI:
             from agent.display import get_tool_emoji
             emoji = get_tool_emoji(function_name)
             label = preview or function_name
-            if len(label) > 50:
-                label = label[:47] + "..."
+            from agent.display import get_tool_preview_max_len
+            _pl = get_tool_preview_max_len()
+            if _pl > 0 and len(label) > _pl:
+                label = label[:_pl - 3] + "..."
             self._spinner_text = f"{emoji} {label}"
             self._invalidate()