feat(lang): module NAME uses A, B - a module reaches only the modules it names

A reference from a module that declares uses into a module it does not
name is refused, exported or not, naming the use and the fix. A module
with no uses clause keeps the old rule; a package's module is always
usable; a friend is not held to it; a cycle in the declared graph is
refused; LUDIC_VIS_REPORT=1 lists the violations as uses: lines. Reseed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/modules/uses.ludic

@@ -0,0 +1,12 @@
+# uses.ludic — L3: `module fishing uses base` names the only modules fishing may reach; the program
+# itself is in no module, so it may call anything exported. A module with no `uses` line keeps the
+# old rule, which is how the rule comes into a codebase one module at a time.
+#
+# Running it prints:  8 3
+import "valley/base"
+import "valley/fishing"
+program Uses {
+  entry {
+    print(`{cast(3)} {bait()}`)
+  }
+}

examples/modules/valley/base/index.ludic

@@ -0,0 +1,5 @@
+# base/index.ludic - a module with no uses line keeps the old rule: its exports are anyone's
+module base
+export function bait() -> int {
+  return 3
+}

examples/modules/valley/fishing/catch.ludic

@@ -0,0 +1,4 @@
+# fishing/catch.ludic - inherits `module fishing uses base` from its barrel
+export function cast(times: int) -> int {
+  return times * bait() - 1
+}

examples/modules/valley/fishing/index.ludic

@@ -0,0 +1,3 @@
+# fishing/index.ludic - fishing names the one module it may reach
+module fishing uses base
+import "catch.ludic"

examples/rejected/uses_cycle.ludic

@@ -0,0 +1,8 @@
+# L3: two modules that each say they use the other are refused, whatever they call
+import "uses_cycle/a"
+import "uses_cycle/b"
+program UsesCycle {
+  entry {
+    print(two())
+  }
+}

examples/rejected/uses_cycle/a/index.ludic

@@ -0,0 +1,5 @@
+# a/index.ludic - a uses b
+module a uses b
+export function one() -> int {
+  return 1
+}

examples/rejected/uses_cycle/b/index.ludic

@@ -0,0 +1,5 @@
+# b/index.ludic - and b uses a: the declared graph goes round
+module b uses a
+export function two() -> int {
+  return one() + 1
+}

examples/rejected/uses_missing.ludic

@@ -0,0 +1,8 @@
+# L3: fishing says `uses base` and calls items.inv_add - exported, but not a module fishing names
+import "uses_valley/items"
+import "uses_valley/fishing"
+program UsesMissing {
+  entry {
+    print(land())
+  }
+}

examples/rejected/uses_valley/fishing/index.ludic

@@ -0,0 +1,5 @@
+# fishing/index.ludic - says it uses base, and then reaches into items
+module fishing uses base
+export function land() -> int {
+  return inv_add(1)
+}

examples/rejected/uses_valley/items/index.ludic

@@ -0,0 +1,5 @@
+# items/index.ludic - exports inv_add, but that is not enough for a module that says `uses`
+module items
+export function inv_add(n: int) -> int {
+  return n + 1
+}