chore(devcontainer): update toolchain to project requirements

[maoyouaa]

What changed

• switch the development container base image from Ubuntu Noble to Ubuntu Resolute
• use Resolute's packaged Go toolchain
• install Clang Format/Tidy 18 and expose their unversioned commands to match CI

Why

The existing development container no longer matches the repository requirements. Ubuntu Noble provides Go 1.22 while the Go test module requires Go 1.25, and the container pins Clang Format/Tidy 14 while x.py requires version 18 or newer.

Impact

Fresh development containers provide the required Go and LLVM tooling, and the default format and tidy commands work without additional path arguments.

Validation

• full docker build of .devcontainer/Dockerfile
• tool smoke check: Go 1.26.0, GCC 15.2.0, Clang Format/Tidy 18.1.8, and minica
• ./x.py build build --unittest --ninja -j 12
• ./x.py test cpp build (600 passed, 1 skipped)
• ./x.py test go build -run TestPing
• ./x.py format
• ./x.py check format
• ./x.py check tidy build -j 12
• git diff --check

Prepared with assistance from OpenAI Codex and verified locally.

[PragmaTwice]

Is it really needed?

[maoyouaa]

You're right — it isn't needed for the default GCC build. It was added after testing an explicit Clang build, so I've removed the global LDFLAGS. A clean GCC 15 build and the tests pass without it.