Bound repeated managed MCP tool calls

[mostlydev]

Summary

• update cllama to skip repeated identical managed tool calls within one mediated turn
• return structured duplicate_tool_call results, record duplicate tool_trace metadata, and surface duplicate metadata through claw audit
• distinguish late stdio MCP responses after cancellation/timeout from truly unknown response IDs
• document the duplicate-call behavior in the managed tools guide and embedded skill text

Tests

• go test ./cmd/claw-mcp-stdio ./internal/audit
• go test ./internal/proxy ./internal/sessionhistory (cllama)
• go test ./...
• go test ./... (cllama)
• go vet ./...
• go vet ./... (cllama)
• go test -tags integration ./...
• go test -tags spike -run ^TestSpikeMCPStdio$ ./cmd/claw/...

Closes #191

Note: this intentionally does not cut a release.