feat(diag): aggregating + filtered trace sinks (histogram, op-filter, per-script)

The existing trace framework only had a flat text formatter, so every question
became 'dump millions of lines, then grep'. This session that cost a long wrong
detour. Add, all observe-only (parity preserved):

- HistogramTraceSink: execution counts per opcode AND per call-site (script:pc)
  with a sample operand. Dumped sorted after the run. This is what instantly
  showed the 493k headless 'sleep's are INPUTNAME.BIN:0x1c3 (a name-entry poll
  loop), not the opening.
- TraceSinkBase: tracks the frame stack -> attributes each step to its REAL
  script (nested call-script frames included) = the 'which script is this pc in?'
  answer a bare step trace can't give.
- TextTraceSink: op-filter (--trace-ops sleep,draw-texture,...) + script:pc tags.
- CompositeTraceSink: fan-out (text + histogram + Godot's call-script queue).
- OpcodeTable.ByLabel: mnemonic -> opcode for --trace-ops.
- CLI: --trace-histogram, --trace-ops, robust --trace-file (mkdir -p).
- Godot: --trace-histogram <file> profiles the REAL run (headless flow diverges:
  real run to page 1 is 562 steps / 0 sleeps vs headless 2M steps / 493k sleeps).
- Also: --sleep-scale <f> debug knob to slow the paced opening for inspection.

Engine 56/56 (4 new); sweep parity 284/13; Godot builds + dogfooded end-to-end.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

engine/Age.Engine/Model/OpcodeTable.cs

@@ -11,4 +11,12 @@ public sealed class OpcodeTable
     }
     public string Label(int op) => _t.TryGetValue(op, out var e) ? e.Label : "";
     public int Argc(int op) => _t.TryGetValue(op, out var e) ? e.Argc : -1;
+
+    /// <summary>Reverse lookup: opcode by mnemonic label (e.g. "sleep" -> 0xc8), or null if none.
+    /// Used by --trace-ops to let a diagnostic filter name ops by mnemonic instead of raw hex.</summary>
+    public int? ByLabel(string label)
+    {
+        foreach (var kv in _t) if (kv.Value.Label == label) return kv.Key;
+        return null;
+    }
 }