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).

tools/code_execution_tool.py

@@ -335,8 +335,8 @@ def _rpc_server_loop(
         if conn:
             try:
                 conn.close()
-            except OSError:
-                pass
+            except OSError as e:
+                logger.debug("RPC conn close error: %s", e)
 
 
 # ---------------------------------------------------------------------------
@@ -550,8 +550,8 @@ def execute_code(
         # Cleanup temp dir and socket
         try:
             server_sock.close()
-        except Exception:
-            pass
+        except Exception as e:
+            logger.debug("Server socket close error: %s", e)
         try:
             import shutil
             shutil.rmtree(tmpdir, ignore_errors=True)