Split test-examples into two phases: build all examples in parallel
first, then run tests serially against pre-built binaries. Abort on any
build failure instead of skipping tests for that example.

Replace the centralized `examples/test-examples.toml` with individual
`test.toml` files in each example directory, updating the test runner
and related documentation accordingly.

scripts

Replace the old run-tools.ps1/run-tools.sh scripts with a new
unified run.ps1/run.sh launcher that supports multiple languages
(PowerShell, Rust, Python, Go, C#, Nim, Perl, Ruby, Zig, and
arbitrary binaries) from the `.run/src/bin` directory.

Move all development tools from `dev_tools/` to `.run/`, update
Cargo workspace config and relevant documentation references.