new: port the meson, cmake and autotools template bodies to manifests

data/templates/meson/manifest.yml

@@ -1,7 +1,15 @@
 ## The `meson` template: a C/C++ project built with Meson through the
-## debhelper meson buildsystem. The logic half — the project() probe, the
-## skeleton bodies and the wizard's pkg-config opt-in (appended to
-## Build-Depends) — lives in src/new/templates/meson.rs.
+## debhelper meson buildsystem. The skeleton bodies below are static data;
+## the logic half — the project() probe and the wizard's pkg-config
+## opt-in (appended to Build-Depends) — lives in src/new/templates/meson.rs.
+##
+## hello.c.tpl is deliberately duplicated (byte-identical) across the
+## makefile, cmake and autotools template directories: every template
+## directory is self-contained — the registry embeds each directory's
+## bodies under its own entry — so a shared body would need
+## cross-directory references the manifest schema has no machinery for.
+## The duplication replaces the Rust hello_c() helper meson.rs used to
+## lend cmake.rs and autotools.rs.
 ##
 ## Schema: see src/new/templates/mod.rs.
 
@@ -13,4 +21,8 @@ build_depends:
   - meson
 architecture: any
 rules_dh_line: "dh $@ --buildsystem=meson"
-files: []
+files:
+  - path: meson.build
+    template: meson.build.tpl
+  - path: hello.c
+    template: hello.c.tpl