Fix ZMQ specialization collision for shared node source scripts in mkconcore

[Titas-Ghosh]

Hi @pradeeban , Fixes #418

This PR fixes a functional bug where mkconcore could generate incomplete ZMQ specialization constants when multiple nodes reference the same source file (for example: A:common.py, B:common.py, C:common.py).

Root Cause

• Specialization was executed per node.
• Output specialization file was keyed by basename (common.py) and reused if it already existed.
• Later node-specific edge params were not merged into the existing specialized file.

What Changed

mkconcore.py

• Build specialization plans per source script instead of per node.
• Merge/deduplicate ZMQ edge parameters for all nodes sharing that script.
• Specialize once per source script, then update all related nodes to that result.

copy_with_port_portname.py

• Added optional output_relpath support so caller can control specialization output path safely.
• Updated CLI usage to accept optional output relative path.

test_cli.py

• Added regression test: test_run_command_shared_source_specialization_merges_edge_params
• Verifies shared common.py includes both PORT_* / PORT_NAME_* definitions from multiple ZMQ edges.

Notes

• No CLI breaking changes.
• No behavior changes for workflows that do not use shared source scripts.
• PR contains only functional code changes related to this fix.