feat(mcpp.plugins): 0.5.0, an island's entry points in the module's namespace (#372)

`docs/42` states one rule for both lanes: the module name and the namespace are
one identifier path. The shader lane followed it and `mcpp.tools.island` did
not, emitting every entry point at global scope, so `import app.kernels` bought
a file name and nothing else. A root's directories now extend the namespace
exactly as a payload tree's do.

The API says roots rather than files: `options::roots` names the directories
implementations live under and `options::layout_root` names the one whose
structure decides where entry points live. `options::strip_prefix` emits a
short spelling beside the authored name, which stays canonical because it is
the symbol.

Breaking for a consumer of `tools-island`, and `latest` moves anyway: every
published consumer pins an exact version, and the three examples in mcpp that
use the generator move to 0.5.0 in the same batch.

The floor stays at mcpp 2026.9.8.1. This changes what the package generates,
not what it asks the engine for.

The CN asset is the same bytes as the GitHub source archive of tag v0.5.0,
sha256 ec11aa99e84d8d003afff9d93a9e76d8b84926ab2586058ee5d51344559777b9,
verified by downloading it back after the upload.

Author: Sunrisepeak

pkgs/m/mcpp.plugins.lua

@@ -2,7 +2,7 @@
 -- each member selected by a feature.
 --
 --   [dependencies.mcpp]
---   plugins = { version = "0.3.0", features = ["rules-spirv"], host-module = true }
+--   plugins = { version = "0.5.0", features = ["rules-spirv"], host-module = true }
 --
 --   // build.mcpp
 --   import mcpp;
@@ -262,6 +262,27 @@
 -- reserved for this package. `mcpplibs:rules-cuda@0.1.0` (pkgs/r/rules-cuda.lua)
 -- stays in the index, superseded by this collection.
 --
+-- 0.5.0 gives an island's entry points the module's own namespace. `docs/42`
+-- states one rule for both lanes -- the module name and the namespace are one
+-- identifier path -- and the shader lane followed it while `mcpp.tools.island`
+-- did not: every entry point was emitted at global scope, so `import
+-- app.kernels` bought a file name and nothing else. A root's directories now
+-- extend the namespace exactly as a payload tree's do.
+--
+-- The API says roots rather than files. `options::roots` names the directories
+-- implementations live under and `options::layout_root` names the one whose
+-- structure decides where entry points live; every other root only has to
+-- define the same names. `options::strip_prefix` emits a short spelling beside
+-- the authored name, which stays canonical because it is the symbol.
+--
+-- It is BREAKING for a consumer of `tools-island`: a qualified name replaces a
+-- global one. Every published consumer pins an exact version, so moving
+-- `latest` breaks none of them, and the three examples in mcpp that use the
+-- generator move to 0.5.0 in the same batch.
+--
+-- The floor does not move. 0.5.0 changes what the package generates, not what
+-- it asks the engine for, so it stays at mcpp 2026.9.8.1.
+--
 -- The descriptor points at the source archive of the tag, the shape `grpcgen`
 -- established; the CN asset is the same bytes, so one sha256 names both.
 package = {
@@ -275,6 +296,13 @@ package = {
 
     xpm = {
         linux = {
+            ["0.5.0"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpp-community/mcpp-plugins/archive/refs/tags/v0.5.0.tar.gz",
+                    CN     = "https://gitcode.com/mcpp-res/mcpp-plugins/releases/download/0.5.0/mcpp-plugins-0.5.0.tar.gz",
+                },
+                sha256 = "ec11aa99e84d8d003afff9d93a9e76d8b84926ab2586058ee5d51344559777b9",
+            },
             ["0.4.0"] = {
                 url = {
                     GLOBAL = "https://github.com/mcpp-community/mcpp-plugins/archive/refs/tags/v0.4.0.tar.gz",
@@ -352,9 +380,16 @@ package = {
                 },
                 sha256 = "adf1f9d6691a5d05a8a4a94e83c733ea39caee1510ce2c9af4cb23bebabea9f5",
             },
-            ["latest"] = { ref = "0.4.0" },
+            ["latest"] = { ref = "0.5.0" },
         },
         macosx = {
+            ["0.5.0"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpp-community/mcpp-plugins/archive/refs/tags/v0.5.0.tar.gz",
+                    CN     = "https://gitcode.com/mcpp-res/mcpp-plugins/releases/download/0.5.0/mcpp-plugins-0.5.0.tar.gz",
+                },
+                sha256 = "ec11aa99e84d8d003afff9d93a9e76d8b84926ab2586058ee5d51344559777b9",
+            },
             ["0.4.0"] = {
                 url = {
                     GLOBAL = "https://github.com/mcpp-community/mcpp-plugins/archive/refs/tags/v0.4.0.tar.gz",
@@ -432,9 +467,16 @@ package = {
                 },
                 sha256 = "adf1f9d6691a5d05a8a4a94e83c733ea39caee1510ce2c9af4cb23bebabea9f5",
             },
-            ["latest"] = { ref = "0.4.0" },
+            ["latest"] = { ref = "0.5.0" },
         },
         windows = {
+            ["0.5.0"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpp-community/mcpp-plugins/archive/refs/tags/v0.5.0.tar.gz",
+                    CN     = "https://gitcode.com/mcpp-res/mcpp-plugins/releases/download/0.5.0/mcpp-plugins-0.5.0.tar.gz",
+                },
+                sha256 = "ec11aa99e84d8d003afff9d93a9e76d8b84926ab2586058ee5d51344559777b9",
+            },
             ["0.4.0"] = {
                 url = {
                     GLOBAL = "https://github.com/mcpp-community/mcpp-plugins/archive/refs/tags/v0.4.0.tar.gz",
@@ -512,7 +554,7 @@ package = {
                 },
                 sha256 = "adf1f9d6691a5d05a8a4a94e83c733ea39caee1510ce2c9af4cb23bebabea9f5",
             },
-            ["latest"] = { ref = "0.4.0" },
+            ["latest"] = { ref = "0.5.0" },
         },
     },