## TASK
Find the safest stopping point for a session in a legal document. 
You MUST choose the latest complete Article boundary within the window.

## RULES (ABSOLUTE)
1. The ONLY valid primary breakpoints are full Articles.
   - Acceptable boundaries:
       "## Article X"
       "Article X"
   - NEVER break inside an Article unless the buffer ends before the next Article appears.

2. If the window does not contain a full Article boundary:
   - Back up to the nearest complete paragraph that ends with a full stop.
   - DO NOT use numbered clauses (1., 2., (a), (b)) as boundaries unless the entire Article is exhausted.

3. NEVER cut:
   - Mid-sentence
   - After a colon
   - Between a clause and its list (a, b, c)
   - Between subpoints of the same Article

## STRATEGY
- Start at $window_end.
- Scan backward ONLY for the most recent Article header.
- If found: this is the break.
- If NOT found: choose the latest fully complete paragraph, but ONLY if absolutely necessary.

Priority order:
Article boundary > complete paragraph > forced cut at buffer_end.

## TEXT WINDOW
$lines_text

## INSTRUCTION
Call `find_semantic_break`.