Engine: extract the CICS transaction map (CSD DEFINE TRANSACTION + START/RETURN/XCTL TRANSID) — the app's entry points #3247

Found while auditing what the #3211 differential covers. The engine builds the internal control-flow graph (COBOL CALL, CICS LINK/XCTL, JCL EXEC PGM= — #3200) and dataset lineage (#3201), but it does not capture the CICS transaction map: which transaction IDs exist and which program each one entry-points into.

The gap

• No CSD/RDO parser — there is no .csd language handler under gitgalaxy/standards/language_standards/languages/, so the resource definitions are never read.
• The corpora ship the definitions, unparsed: app/csd/CARDDEMO.CSD, app/app-vsam-mq/csd/CRDDEMOM.csd (carddemo), etc/install/base/installjcl/BANK.csd (CBSA) — all full of DEFINE TRANSACTION(xxxx) PROGRAM(yyyy) ....
• The COBOL routes control by transaction too: EXEC CICS RETURN TRANSID('OCCS'), START TRANSID, XCTL ... , RUN TRANSID. Today those are only counted as arch_concurrency / arch_ipc signals, not turned into edges.

Why it matters

In a CICS application the transaction is the front door: a terminal/user submits a 4-character transaction ID and CICS routes it to a program. Without the transaction map we have the internal call graph but not the external entry points — we can see how programs call each other, but not what a user can actually invoke, nor which flow each screen/transaction starts. For "we understand the structure of a CICS repo" this is the missing top layer, and it's what a modernizer needs to define service/API boundaries (each transaction ≈ a candidate endpoint).

Scope sketch

1. Parse the CSD (.csd, and DEFINE TRANSACTION/DEFINE PROGRAM in DFHCSDUP JCL input): a csd language handler that yields transaction → program (and PROFILE/GROUP) resources into the master DB.
2. Extract the in-source routing as edges: EXEC CICS RETURN/START/XCTL/RUN TRANSID(...) transaction targets (literal, or via working-storage VALUE like the Mainframe call graph: no edges for COBOL CALL, CICS LINK/XCTL or JCL EXEC PGM=, and unresolved CALL targets are recorded nowhere #3200 CALL resolution), joined to the CSD map so a transaction resolves to its program.
3. Expose it through galaxy_ir (e.g. EngineFile/GalaxyIR.transactions and edge_kind transaction), and add answer-key coverage so the Refraction differential: classify every delta by cause and gate on an unexplained count #3211 differential can grade it like units/copybooks/lineage.

Acceptance

refraction_differential.py --corpus reports transactions as a compared datum, and the refraction pipeline can name each program's entry transaction(s) — the basis for service/endpoint boundaries in the generated tree.

Sibling of #3246 (data-division items); part of epic #3122.