Bug_094_MUST_FIX — VND-NOTES-010: update_vendor_agent_notes accepts tab-only notes

[steadhac]

Component: finbot/tools/data/vendor.py → update_vendor_agent_notes
Root cause:

# No content check — "\t" passes through
new_notes = f"{existing_notes}\n\n{agent_notes}"   # ← produces "\n\n\t"

Steps to reproduce:

1. Create a vendor
2. Call update_vendor_agent_notes(vendor.id, "\t", session)

Expected behavior: ValueError raised — tab-only notes carry no meaningful content
Actual behavior: Tab character appended to vendor notes

How to execute:

pytest tests/unit/tools/test_vendor.py::TestUpdateVendorAgentNotes::test_vnd_notes_010_tab_only_notes_accepted_without_validation -v

Proposed fix:

if not agent_notes or not agent_notes.strip():
    raise ValueError("agent_notes must not be empty or whitespace-only")

Impact:
Confirms the whitespace guard must use .strip() (which catches tabs) rather than only checking for space characters.

Acceptance criteria:

• "\t", "\t\t" raise ValueError
• "Vendor reviewed" is accepted

[mekaizen]

@saikishu picking this please assign