Migrate COBOL scaffolding templates to Java (java/ Maven module)

[devin-ai-integration]

Summary

Adds a new top-level java/ Maven module containing Java equivalents of the four COBOL scaffolding templates in src/templates/ (originals untouched, kept for benchmark comparison). Base package com.cog.clbs, JDK 17, JUnit 5.

Mapping (full table in java/README.md):

• standard-program.cbl → AbstractProgram (final run() drives initialize() → execute() loop until end-of-file → terminate(), with handleError() defaulting to RC 8) + ReturnCode enum for the RC 0/4/8/12/16 framework; setReturnCode never lowers severity.
• file-handling.cbl → VsamFile<V> (TreeMap-backed KSDS: read/write/rewrite/delete/readNext with FileStatus codes '00'/'10'/'22'/'23') and SequentialFile (line-record I/O with AT-END semantics).
• db2-handling.cbl → Db2Handler over JDBC (connect/attach, PreparedStatement as host variables, ResultSet as cursor, commit/rollback, CONNECT RESET → disconnect()) + SqlCodeException carrying SQLCODE.
• error-handling.cbl + ERRHND.cpy/ERRHNDL.cbl → ErrorHandler (severity counts, P300-style message formatting, P400 action determination, 8000-CHECK-FINAL-STATUS → finalReturnCode()), ErrorRecord mirroring the copybook fields, ErrorSeverity (F/W/I) and ErrorAction (R/C/A) enums.

mvn compile and mvn test pass (17 smoke tests across the four components).

Link to Devin session: https://app.devin.ai/sessions/47f444e0c8ab4288978a21d976e479d6

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End-to-end test results for the java/ scaffolding module ✅

Ran a clean build/test plus an adversarial runtime harness against the compiled classes (JDK 21, Maven 3.6.3).

• mvn clean test: BUILD SUCCESS — Tests run: 17, Failures: 0, Errors: 0, Skipped: 0 (AbstractProgramTest 4, Db2HandlerTest 3, ErrorHandlerTest 7, FileHandlingTest 3)

Adversarial runtime checks (24/24 passed)

• VsamFile: duplicate WRITE → DUPLICATE_KEY (22); READ missing key → empty + RECORD_NOT_FOUND (23); READ NEXT past last key → END_OF_FILE (10); op before OPEN → FILE_NOT_OPEN; REWRITE/DELETE missing → RECORD_NOT_FOUND
• SequentialFile: OPEN OUTPUT/WRITE/CLOSE, reopen INPUT, reads return records in order, read past last → empty + END_OF_FILE (10) (AT END)
• ErrorHandler: FATAL → ABEND + abendRequested + final RC SEVERE (12); recordError → RC ERROR (8); WARNING → CONTINUE + RC WARNING (4); clean → RC SUCCESS (0); message formatted Error in PGM1 - boom (T123)
• AbstractProgram: normal lifecycle → RC 0; execute() throwing → RC 8 via 9000-HANDLE-ERROR path; RC never lowered (12 then 4 → stays 12)

Not covered: Db2Handler against a live JDBC database (no DB in the test environment; verified via its unit tests only).

Tested by Devin — session