fix: bound Claude Code transcript discovery

[0xernesto]

Summary

• stop Claude Code transcript discovery from falling back to a full home-directory crawl when the default home search root lacks the known Claude metadata directory
• keep discovery bounded to ~/Library/Application Support/Claude/claude-code-sessions for default macOS home-root polling
• add an infrastructure regression test that places a fake local_*.json under a home subdirectory such as Contacts and verifies discovery ignores it

Why

The background episode_sync poller can invoke Claude Code discovery from the default home search root. If the known Claude metadata directory is absent, the old fallback recursively scanned the entire home directory. On macOS this can trigger repeated TCC privacy prompts for protected locations such as Contacts, Desktop, or other app data.

Tests

• .venv/bin/python -m pytest tests/infrastructure/test_claude_code_discovery.py
• .venv/bin/python -m pytest tests/infrastructure

[cucupac]

LGTM.