chore: import upstream snapshot with attribution

docs/articles/building-from-source.md

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+## Use A Checkout Compiler
+
+Use this page when you are working on Zerolang itself or testing a local compiler
+change. Public docs use `zero`; contributor notes cover checkout wrapper
+details.
+
+## Build
+
+```sh
+pnpm install
+make -C native/zero-c
+zero --version
+```
+
+## Focused Loop
+
+```sh
+zero check examples/hello.graph
+zero run examples/add.graph
+zero build --emit exe --target linux-musl-x64 examples/add.graph --out .zero/out/add
+```
+
+Inspect graph and size facts:
+
+```sh
+zero inspect --json examples/systems-package
+zero size --json examples/point.graph
+zero targets
+```
+
+Explain diagnostics:
+
+```sh
+zero explain TAR002
+zero explain --json TYP009
+```
+
+## Validation
+
+```sh
+pnpm run conformance
+pnpm run command-contracts:local
+pnpm run native:test
+pnpm run docs:build
+```
+
+Before ending an agent turn that changed the repository, run
+`pnpm run conformance`.
+
+## Native Targets
+
+The documented native target names are:
+
+- `darwin-arm64`
+- `darwin-x64`
+- `linux-arm64`
+- `linux-musl-arm64`
+- `linux-musl-x64`
+- `linux-x64`
+- `win32-arm64.exe`
+- `win32-x64.exe`
+
+Unsupported target or feature requests report diagnostics instead of silently
+choosing another backend.