Add tests for loadEntries and countEntries with malformed history lines

[404-Page-Found]

Task summary

Add tests that verify loadEntries() and countEntries() behavior when history.jsonl contains malformed JSON lines mixed with valid entries.

Why this is a good first issue

The parser logic is simple, and this task is a contained test addition with clear expected outcomes.

Suggested files or areas

• src/history/store.ts
• tests/history-profile.test.mjs or a new history-store focused test file

Acceptance criteria

• Add a test that confirms malformed lines are skipped by loadEntries() while valid lines are returned.
• Add/clarify expected behavior for countEntries() with malformed lines.
• Keep existing history/profile tests passing.
• Document assumptions in test names/comments.

Extra context

loadEntries() currently catches JSON parse errors and returns only valid entries, but this behavior should be explicitly regression-tested.