docs: restore detailed design documents

Restored the following documents that were removed in Black-white-box-Merge:
- docs/detailed-design/ (9 detailed design documents + append_doc.py)
- docs/development-paradigm.md (development paradigm flowchart)
- docs/test-report.md (test report)
- AGENTS.md (project instructions)
- _AI_USAGE_LOG.md (AI usage log)
- CLAUDE.md (project instructions)
- sample/ (4 example files)

sample/simple.cbl

@@ -0,0 +1,16 @@
+       IDENTIFICATION DIVISION.
+       PROGRAM-ID. SIMPLE.
+       DATA DIVISION.
+       WORKING-STORAGE SECTION.
+       01 BILL-RECORD.
+          05 BR-AMT    PIC S9(7)V99 COMP-3.
+          05 BR-STATUS PIC X.
+          05 BR-DATE   PIC 9(8).
+       PROCEDURE DIVISION.
+           MOVE 1500 TO BR-AMT.
+           MOVE 'A' TO BR-STATUS.
+           MOVE 20260522 TO BR-DATE.
+           DISPLAY BR-AMT
+           DISPLAY BR-STATUS
+           DISPLAY BR-DATE
+           STOP RUN.