feat: summarize oversized tool payloads in investigation prompts

[manthan787]

Summary

• add prompt-payload normalization to cap oversized tool outputs before they are injected into triage/evidence prompts
• bound strings, arrays, objects, and nesting depth to keep prompt size predictable while preserving useful structure
• apply summarized payload formatting to triage context gathering and evidence evaluation prompt construction
• add tests covering truncation behavior for large tool payloads

Validation

• npm run test -- src/agent/__tests__/investigation-orchestrator.test.ts
• npm run typecheck