fix(loop): avoid DB tool_call ID collisions from provider IDs

[ChristmasSun]

Summary

Fix a persistence bug where provider tool call IDs were being reused as tool_calls.id primary keys.

The loop was overwriting internally generated ULIDs with provider IDs before DB insert. Provider IDs are not guaranteed globally unique across turns, which can trigger:
UNIQUE constraint failed: tool_calls.id

Changes

• Keep internal ULID-based ToolCallResult.id in the loop.
• Do not overwrite it with inference/provider tc.id.
• Add regression test that reuses the same provider tool-call ID across multiple turns and verifies persisted IDs remain unique.

Testing

• npx vitest run src/__tests__/loop.test.ts
• npm test (26 files, 991 tests, all pass)