cmd: build local package graphs

docs/build-system.md

@@ -2770,6 +2770,59 @@ The replacement deletes these concepts rather than emulating them indefinitely:
 There will be no compatibility alias that silently translates an old import,
 interface, workdir, or link search into the new model.
 
+### 11.6 Implemented local package slice
+
+The first executable package slice is intentionally smaller than the final
+module design above. It is local, offline, and manifest-free. The supported
+form is:
+
+```sh
+out/bin/ww build -I /work/acme -o app /work/acme/cmd/app
+```
+
+Every selected source uses the existing syntax:
+
+```ww
+package main;
+import lib.math;
+```
+
+An import is translated from dots to path separators and resolved, with
+directory packages preferred, through the entry package's directory, explicit
+`-I` roots in command order, and the toolchain source-library root. There is no
+network or manifest fallback. The loader uses the compiler frontend's
+imports-only parser, unions duplicate imports, byte-sorts direct edges, interns
+resolved directories by filesystem identity, and reports self-imports and
+stable cycle chains before compilation.
+
+A directory package consists of its immediate regular non-symlink `.ww` files,
+excluding `*_test.ww`, in byte-sorted filename order. Every selected file must
+declare the same package. An imported directory's declared package must equal
+the final component of its import path; two logical identities for one physical
+directory are rejected rather than compiled twice.
+
+Packages compile serially in dependency-first postorder. The compiler emits the
+existing deterministic `.wwi` interface for every importable package and only
+exported declarations enter that interface. A source qualifier is visible only
+when its owning package directly imports it; private members and transitive-only
+qualifiers are compiler errors. For compatibility with public signatures that
+name deeper types, composed compiler units still carry transitive interface type
+facts for internal resolution, but those facts do not create source-visible
+bare names, package qualifiers, or value bindings. Replacing that
+source-like closure with a self-contained typed export encoding remains part of
+the later export-format work, not package-loader semantics.
+
+An ordinary root is linked with the full reachable object closure into the
+requested executable (legacy WW programs may use a package name other than
+`main`). `ww build -p -o lib.a DIR` explicitly requests a non-main package
+product: it emits a deterministic archive at `lib.a` and its compiler interface
+at `lib.a.wwi`, without invoking the linker. A logical target retains its full
+identity (`ww build -p -I ROOT -o bar.a foo.bar` emits `foo.bar.*` symbols),
+while a literal directory uses its declared leaf package. Package output
+requires a directory and `-p` cannot be combined with assembly-only `-S`. Two
+cold builds with identical inputs are required to produce byte-identical
+requested products.
+
 ## 12. Candidate architectures and hard-gate decision
 
 Five candidates were developed as coherent systems, not as feature bins.