fix: replace silent exception swallowing with debug logging across tools

Add logger.debug() calls to 27 bare 'except: pass' blocks across 7 core
files, giving visibility into errors that were previously silently
swallowed. This makes it much easier to diagnose user-reported issues
from debug logs.

Files changed:
- tools/terminal_tool.py: 5 catches (stat, termios, fd close, cleanup)
- tools/delegate_tool.py: 7 catches + added logger (spinner, callbacks)
- tools/browser_tool.py: 5 catches (screenshot/recording cleanup, daemon kill)
- tools/code_execution_tool.py: 2 remaining catches (socket, server close)
- gateway/session.py: 2 catches (platform enum parse, temp file cleanup)
- agent/display.py: 2 catches + added logger (JSON parse in failure detect)
- agent/prompt_builder.py: 1 catch (skill description read)

Deliberately kept bare pass for:
- ImportError checks for optional dependencies (terminal_tool.py)
- SystemExit/KeyboardInterrupt handlers
- Spinner _write catch (would spam on every frame when stdout closed)
- process_registry PID-alive check (canonical os.kill(pid,0) pattern)

Extends the pattern from PR #686 (@aydnOktay).

agent/display.py

@@ -5,6 +5,7 @@ Used by AIAgent._execute_tool_calls for CLI feedback.
 """
 
 import json
+import logging
 import os
 import sys
 import threading
@@ -14,6 +15,8 @@ import time
 _RED = "\033[31m"
 _RESET = "\033[0m"
 
+logger = logging.getLogger(__name__)
+
 
 # =========================================================================
 # Skin-aware helpers (lazy import to avoid circular deps)
@@ -362,7 +365,7 @@ def _detect_tool_failure(tool_name: str, result: str | None) -> tuple[bool, str]
             if exit_code is not None and exit_code != 0:
                 return True, f" [exit {exit_code}]"
         except (json.JSONDecodeError, TypeError, AttributeError):
-            pass
+            logger.debug("Could not parse terminal result as JSON for exit code check")
         return False, ""
 
     # Memory-specific: distinguish "full" from real errors
@@ -372,7 +375,7 @@ def _detect_tool_failure(tool_name: str, result: str | None) -> tuple[bool, str]
             if data.get("success") is False and "exceed the limit" in data.get("error", ""):
                 return True, " [full]"
         except (json.JSONDecodeError, TypeError, AttributeError):
-            pass
+            logger.debug("Could not parse memory result as JSON for capacity check")
 
     # Generic heuristic for non-terminal tools
     lower = result[:500].lower()

agent/prompt_builder.py

@@ -159,8 +159,8 @@ def _read_skill_description(skill_file: Path, max_chars: int = 60) -> str:
             if len(desc) > max_chars:
                 desc = desc[:max_chars - 3] + "..."
             return desc
-    except Exception:
-        pass
+    except Exception as e:
+        logger.debug("Failed to read skill description from %s: %s", skill_file, e)
     return ""