Add Subsystem D (SHA01-10): social insurance subsystem + design-resource consistency fixes

- Add SHA01CVT-SHA10S10: all 10 programs, COPY books (13), binaries,
  design docs, resource usage lists, DDL schema_sha.sql
- Add KYU01REC-KYU06REC COPY books (previously missing from git)
- Fix design-code inconsistencies detected in audit:
  - SHA07KBR: remove dead SHACHKAC COPY (SUB04CHK never called)
  - SHA02MNC: 2020TYPSOR paragraph -> inline EVALUATE; SUB04CHK = PARM val
  - SHA05TWN: REVISED-TYPE values 'C'/'N' -> 'A'(定期決定)/'B'(月変)
  - SHA03MNP: 2010CALCSOR/2020WRTSOR -> inline implementation
  - SHA04TWO: remove GRADE-HISTORY from DB table list (not accessed)
  - SHA06TWM: add SALARYDB.EMP-MASTER to DB table list
  - SHA10S10: fix error file W99OUTFIL, 10+1 file count
- Fix comment column alignment (Area A col 7) in SHA07KBR, SHA08SRT
- Update KYU source/design docs: BOM removal, classification comment cleanup
- Update README: Subsystem D added, program count 39

cpy/KYU04REC.cpy

@@ -0,0 +1,16 @@
+      * SALARY-NET / DEPT-OUT 差引支給額レコード 200B
+      * KYU05DED出力 / KYU07DIV・KYU08PRI・KYU09MRG・KYU06UPD入力
+             03  (A)EMP-ID           PIC X(008).
+             03  (A)REC-TYPE         PIC X(001).
+             03  (A)EMP-NAME         PIC X(040).
+             03  (A)DEPT-CODE        PIC X(002).
+             03  (A)REGION-CODE      PIC X(002).
+             03  (A)CATEGORY-CODE    PIC X(003).
+             03  (A)GROSS-PAYMENT    PIC 9(009).
+             03  (A)INCOME-TAX       PIC 9(009).
+             03  (A)INSURANCE        PIC 9(009).
+             03  (A)RESIDENT-TAX     PIC 9(009).
+             03  (A)NET-PAYMENT      PIC 9(009).
+             03  (A)TAXABLE-INCOME   PIC 9(009).
+             03  (A)PAY-AMOUNT       PIC 9(009).
+             03  FILLER              PIC X(081).