build: route .ww directories as packages

docs/spec.md

@@ -358,6 +358,22 @@ ImportPath    = ident { "." ident } .
   symbol, `.wwi`, publication, or persistence identity. Build workdir format
   remains 18, test workdir format remains 19, and semantic storage format
   remains 3.
+- A local literal passed to `ww build` whose requested final basename ends
+  `.ww` remains a directory request when ordinary `stat` reports a directory,
+  including when the spelling is a symlink or ends `_test.ww`. The directory
+  target therefore bypasses raw named-source prefix and test-source
+  classification and enters ordinary directory enumeration. Actual eligible
+  production entries, package declarations, imports, graph actions, producers,
+  output policy, publication, persistence, invalidation, rollback, and cleanup
+  are exactly those of the existing directory package route. The requested
+  spelling and physical target are loader/presentation metadata only and create
+  no new package, dotted-import, graph, action, symbol, artifact, `.wwi`,
+  publication, or persistence identity. Raw `ww test`, `ww test -c`, and
+  `ww test -S` already use the same directory classification and are unchanged.
+  `ww run` retains its separate named-operand front door. Multiple operands,
+  recursive and logical requests, regular and non-regular source targets, and
+  dangling symlinks are not changed. Build workdir format remains 18, test
+  workdir format remains 19, and semantic storage format remains 3.
 - `import acme.codec;` loads the canonical package `acme.codec`. If that
   package declares `package wire;`, the importing file sees its exported names
   as `wire.Name`; `codec.Name` is not an additional binding. An explicit alias
@@ -465,14 +481,24 @@ ImportPath    = ident { "." ident } .
   the action list; non-main command dependencies retain ordinary actions, and
   a selection containing no command rejects before tools or output creation.
   A raw command-line `.ww` source uses its source basename without `.ww`, and
-  a raw non-main source is the same no-command rejection. Missing
-  trailing-slash hierarchies are created transactionally from `0777`, filtered
-  by the caller's umask.
+  a raw non-main source is the same no-command rejection. An existing
+  directory whose requested basename ends `.ww` is not such a raw source: it
+  retains directory-package output naming. With no `-o`, its requested leaf
+  is used verbatim (for example, `directory_test.ww`); with an existing
+  output-directory `-o`, publication instead uses the canonical selected
+  target leaf (for example, `directory-target`).
+  Missing trailing-slash hierarchies are created transactionally from `0777`,
+  filtered by the caller's umask.
   Loading and package/import diagnostics precede no-main, derived-path,
   duplicate-destination, implicit-default, and other output preflight; all of
-  those checks precede creation. Producer failure or interruption preserves
-  existing directory contents and removes only request-created prefixes and
-  stages. A non-directory output retains the single-product file/archive rule.
+  those checks precede creation. Producer failure and coordinator-owned
+  interruption preserve existing directory contents and remove only
+  request-created prefixes and stages. Direct external `SIGTERM` of a build
+  driver is a verified-open exception: both stages preserve public and
+  committed work bytes and reap their process group, but may leave `.new`
+  staging files that make a later persistent-work request reject until those
+  files are removed. A non-directory output retains the single-product
+  file/archive rule.
   If a lone
   command's synthesized default basename already names a directory, loading
   and graph validation complete and the build rejects before tools without