fix(pi): preserve tool result outcomes

[drewstone]

Summary

• join Pi message-level tool results to their calls by call ID
• preserve result output, completion time, success or failure status, and error text
• keep unfinished calls UNSET and retain unmatched results as explicitly marked root-owned tool spans
• preserve the tool-argument capture merged in fix(pi): preserve tool call arguments #52

Root cause

Pi stores calls inside assistant message content, but stores their completions as separate role: "toolResult" messages. The adapter only handled result blocks nested inside message content, so message-level results were treated as model messages and their output, status, and timing were lost.

Impact

Pi traces now represent successful, failed, unfinished, out-of-order, and orphaned tool outcomes without inventing model calls or dropping result evidence.

Validation

• pnpm vitest run tests/adapters.test.ts -t 'pi tool results' — 4 passed
• pnpm typecheck — passed
• pnpm test — 371 passed
• pnpm build — passed
• pnpm check:package — passed
• git merge-tree --write-tree origin/main HEAD — clean