ww package: reject non-function main declarations

docs/spec.md

@@ -307,9 +307,17 @@ ImportPath    = ident { "." ident } .
   ownership, symbols, artifacts, storage, or diagnostics. Repeated occurrences
   of the same exact identity remain valid and deduplicate normally.
 - An executable package is one declared `package main` and containing a
-  `fn main`; path and directory spelling do not classify commands. An ordinary
-  import of a package declared `main` is rejected, except for the toolchain's
-  colocated external-test wiring.
+  `fn main`; path and directory spelling do not classify commands. Within a
+  package declared `main`, a package-scope declaration named `main` must be a
+  function: `let`, `const`, `def`, and `type` forms reject as
+  `cannot declare main - must be func` and do not enter package scope. The
+  restriction depends only on the declared package name. A package with any
+  other declared name may use or export `main` regardless of its dotted import
+  path, path leaf, physical directory, or selection role. WW retains its
+  established program-entry ABI, so a function `main` may carry WW's supported
+  arguments and result; this rule does not adopt Go's source signature. An
+  ordinary import of a package declared `main` is rejected, except for the
+  toolchain's colocated external-test wiring.
 - For `ww build`, an explicit `-o` names an output directory when ordinary
   `stat` reports an existing directory (following symlinks) or its spelling
   ends in `/`. This classification is independent of whether one or many
@@ -414,6 +422,13 @@ called as `init()`, selected as `pkg.init`, exported, or used by another kind
 of declaration. Package-variable initialization completes before these
 functions run.
 
+In a package whose declared name is `main`, only a function declaration may
+claim the package-scope name `main`. A rejected non-function declaration is not
+installed and cannot satisfy the executable entry. This is independent of
+canonical import identity and physical location. The accepted function shape
+continues to use WW's entry ABI, including its supported argument and result
+forms.
+
 ### 5.2 `let`
 
 ```
@@ -697,6 +712,12 @@ under test binds to the augmented white-box action when it exists; affected
 transitive importers are copied and rewired so ordinary and augmented package
 state do not coexist in the linked closure.
 
+A non-function package-scope `main` in production or same-package test source
+of a package declared `main` is a package-checker failure. Generated test-main
+ownership does not hide or replace it: the product is not linked or executed,
+no test accounting or package `ok` result is emitted, and ordinary build/test
+failure presentation and rollback apply.
+
 Those variants are action distinctions over exact package representatives, not
 new ordinary package identities for case-fold comparison. Production,
 same-package test, external test, and recompiled copies of one exact canonical