Add UVM integration guide and SystemVerilog UVM kernel code for CHIron

[Copilot]

Summary

Adds markdown documentation and a complete SystemVerilog UVM testbench skeleton showing how to use CHIron as the protocol kernel of a UVM-based AMBA CHI verification environment.

Changes

Documentation (docs/)

• docs/uvm_integration_guide.md — Comprehensive guide covering:

  • Architecture diagram (CHIron C++ kernel ↔ UVM via DPI-C)
  • Step-by-step setup: configure parameters, build DPI-C shim, connect DUT, enable CLog logging, write sequences, run simulation (VCS/Xcelium/Questa commands)
  • How to extend the reference model using CHIron's Xact::Router and XactionAllocatingRead etc.
  • CHI Issue E/EB/B support matrix and known limitations
  • Full file reference table

• docs/uvm_quickstart.md — 5-minute quickstart: clone → build → connect DUT → run → inspect CLog

SystemVerilog UVM Code (uvm/)

File	Purpose
chi_pkg.sv	SV package: CHI Issue E parameters, REQ/RSP/DAT/SNP opcodes, packed flit structs, helper functions
chi_if.sv	Parameterised CHI bus interface with rn_driver_cb and monitor_cb clocking blocks
chi_seq_item.sv	UVM sequence item: all 6 CHI channel fields + raw 512-bit flit (for CLog) with correct position-tracked pack_req()
chi_driver.sv	Credit-aware UVM driver for TXREQ / TXRSP / TXDAT channels
chi_monitor.sv	Passive monitor for all 6 channels with inline CLog.B DPI-C logging
chi_agent.sv	UVM agent (active/passive)
chi_scoreboard.sv	Protocol checker that forwards every flit to the CHIron reference model via DPI-C
chi_coverage.sv	Functional coverage: REQ opcode × size × NS, RSP opcode × resp × resp_err, SNP opcode × RetToSrc, QoS × channel
chi_seq_lib.sv	Built-in sequences: ReadShared, ReadUnique, WriteUniqueFull, WriteBackFull, AtomicSwap, SnpResp, randomised mix
chi_env.sv	UVM environment wiring agent → scoreboard + coverage
chi_test.sv	chi_read_test, chi_write_test, chi_rand_test
chi_top.sv	Top-level testbench (clock/reset, DUT hook, run_test())
chi_refmodel_dpi.cpp	C++ DPI-C shim skeleton wrapping CHIron FlitConfiguration / Xaction classes

Security Summary

No security vulnerabilities found. CodeQL analysis returned 0 alerts. The C++ DPI-C shim validates flit lengths before accessing memory.