Add GCC 12+ requirement documentation with Ada URL parser context

[Copilot]

Users attempting to build Zeno on Ubuntu 22 LTS (GCC 11) and Ubuntu 20 LTS (GCC 10) encounter compilation failures due to missing C++20 constexpr support in older GCC versions. The errors manifest as:

ada.h:6617:10: error: call to non-'constexpr' function 'std::__cxx11::basic_string<...>::operator std::basic_string_view() const'

This occurs because the ada-url/goada dependency requires C++20 constexpr features that were not available in GCC 11 and earlier versions.

While the CI already handles this requirement by explicitly installing g++-12, users were not informed about this prerequisite, leading to build failures on common LTS distributions.

Changes made:

• Added a "Requirements for Building" section to README.md documenting Go 1.25+ and GCC 12+ requirements
• Included explanation about C++20 constexpr support needs
• Enhanced CGO requirement explanation to clarify it's needed for Go bindings to Ada (the WHATWG URL parser) via github.com/ada-url/goada
• Added note about future plans to move to a pure Go alternative
• Updated .github/copilot-instructions.md to specify GCC 12+ for development documentation
• Added note about Ubuntu 22 LTS and earlier requiring newer GCC installation

The documentation now clearly informs users about build requirements upfront, preventing confusion and failed build attempts, while providing context about why the C++ dependency exists and that it's temporary.

Fixes #462.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.20%. Comparing base (330cc91) to head (7f63c07).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #463      +/-   ##
==========================================
- Coverage   56.25%   56.20%   -0.05%     
==========================================
  Files         130      130              
  Lines        8037     8037              
==========================================
- Hits         4521     4517       -4     
- Misses       3157     3161       +4     
  Partials      359      359              

Flag	Coverage Δ
e2etests	40.50% <ø> (-0.05%)	⬇️
unittests	29.24% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[CorentinB]

@copilot explain in the README that we need CGO because of the Go bindings of Ada, the WHATWG URL parser https://github.com/ada-url/goada, and that we hopefully will move away from it for a pure Go alternative in the future.

[Copilot]

@copilot explain in the README that we need CGO because of the Go bindings of Ada, the WHATWG URL parser https://github.com/ada-url/goada, and that we hopefully will move away from it for a pure Go al...

Updated the README to explain that CGO is needed for Go bindings to Ada (the WHATWG URL parser) via github.com/ada-url/goada, and added note about future plans to move to a pure Go alternative. Changes in commit 66be986.

[NGTmeaty]

requirements for building

[CorentinB]

@copilot listen to the man

[Copilot]

Updated the section title from "Requirements" to "Requirements for Building" to clarify that these are specifically build requirements. Changes in commit bd25f88.