fix: preserve grep and ls tool results

[lawyer112]

What changed

• Preserve actual grep matches, file lists, counts, and truncation metadata in replayed tool results.
• Preserve the supplied ls directory tree instead of reducing it to path and file-count metadata.
• Bound replay payloads to 64 KiB and clearly report incomplete or truncated results.
• Add coverage for grep content, file-list, count, and ls tree summaries.

Why

Successful grep and ls tool calls were previously summarized as metadata-only strings. On the next model pass, the assistant could see that a tool succeeded but not the files, matches, or directory entries it needed to continue.

Impact

The model receives the useful contents of successful search and listing calls, while payload limits still prevent oversized replay messages.

Validation

• go test ./...
• Production candidate built and verified locally on the formal 18080/18090 runtime.