[Feature]: Add CI pipeline for RISC-V / RVV

[ihb2032]

Problem / Motivation

As zvec involves performance-critical vector operations, supporting RISC-V Vector Extensions is a highly valuable capability. However, without a dedicated CI pipeline for the RISC-V architecture, any new commits to the C++ core might inadvertently break RVV optimizations, cause compilation failures on RISC-V targets, or introduce silent logic regressions.
Relying on developers to manually cross-compile and test RVV implementations locally before releases is prone to human error and slows down the development cycle. Having an automated CI workflow ensures that RVV code paths are continuously verified.

Proposed Solution

Alternatives Considered

No response

Affected Area

No response