new: port the shell, empty, makefile and go templates to manifests

Move the four templates' static file bodies into .tpl files under
data/templates/<id>/, referenced by their manifests' files: lists —
the shell skeleton script (executable, {command}-named) with its
skeleton-only debian/install mapping, the empty template's stub README,
the makefile hello.c/Makefile skeleton with its skeleton-only install
mapping, and go's go.mod/main.go skeleton (the go directive of go.mod
stays a literal: nothing about it is answer-derived).

The empty template ends up hookless — zero Rust, its registry entry
points at no hooks — and src/new/templates/empty.rs is deleted. The
shell and go hooks shrink to their probes (plus go's {go_import_path}
context value); the makefile hooks keep only the existing-tree hint
probing the packaged Makefile for a phony install: target, since that
heuristic reads the tree and cannot be data.

data/templates/empty/README.tpl

@@ -0,0 +1 @@
+{name} - empty base tree scaffolded by `pkh new`; there is intentionally no upstream build system here.

data/templates/empty/manifest.yml

@@ -1,6 +1,9 @@
 ## The `empty` template: a metapackage (non-empty Depends list) or an
 ## empty base package with no build system at all — pure `dh $@` plumbing
-## as a starting point for hand-written rules.
+## as a starting point for hand-written rules. Pure data: no hooks, the
+## metapackage Depends payload travels in the wizard answers, and the
+## only upstream file is the stub README marking the tree as
+## intentionally empty.
 ##
 ## Schema: see src/new/templates/mod.rs.
 
@@ -11,4 +14,6 @@ detect:
 build_depends: []
 architecture: all
 rules_dh_line: "dh $@"
-files: []
+files:
+  - path: README
+    template: README.tpl

data/templates/go/go.mod.tpl

@@ -0,0 +1,3 @@
+module {name}
+
+go 1.21

data/templates/go/main.go.tpl

@@ -0,0 +1,8 @@
+// Placeholder for {name}, generated by `pkh new`.
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("Hello from {command}!")
+}

data/templates/go/manifest.yml

@@ -1,6 +1,8 @@
 ## The `go` template: a Go module built through dh-golang. The logic half
 ## — the go.mod module-line probe and the `{go_import_path}` value below —
-## lives in src/new/templates/go.rs.
+## lives in src/new/templates/go.rs; the skeleton bodies are static data
+## (the `go` directive of go.mod stays a literal: nothing about it is
+## answer-derived, so it has no {placeholder}).
 ##
 ## Schema: see src/new/templates/mod.rs.
 
@@ -15,4 +17,8 @@ architecture: any
 rules_dh_line: "dh $@ --buildsystem=golang"
 source_fields:
   XS-Go-Import-Path: "{go_import_path}"
-files: []
+files:
+  - path: go.mod
+    template: go.mod.tpl
+  - path: main.go
+    template: main.go.tpl

data/templates/makefile/Makefile.tpl

@@ -0,0 +1,16 @@
+CC ?= cc
+CFLAGS ?= -O2 -Wall -Wextra
+PREFIX ?= /usr
+
+all: {command}
+
+{command}: hello.c
+	$(CC) $(CFLAGS) -o $@ hello.c
+
+install: {command}
+	install -Dm755 {command} $(DESTDIR)$(PREFIX)/bin/{command}
+
+clean:
+	rm -f {command}
+
+.PHONY: all install clean

data/templates/makefile/hello.c.tpl

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+/* Placeholder for {name}, generated by `pkh new`. */
+int main(void)
+{
+	printf("Hello from {command}!\n");
+	return 0;
+}

data/templates/makefile/install.tpl

@@ -0,0 +1 @@
+{command} usr/bin/{command}

data/templates/makefile/manifest.yml

@@ -2,7 +2,11 @@
 ## debhelper's makefile buildsystem runs `make` for the build and
 ## `make install DESTDIR=...` when the Makefile carries an `install:`
 ## target (missing targets are skipped gracefully), so plain `dh $@`
-## plumbing is enough here.
+## plumbing is enough here. The phony-install hint of
+## src/new/templates/makefile.rs (whether dh_auto_install will run
+## `make install` for an existing tree) is the only logic; the skeleton
+## bodies below are static data (the install mapping is rendered for
+## skeletons only, whose phony install target is known by construction).
 ##
 ## Schema: see src/new/templates/mod.rs.
 
@@ -14,4 +18,11 @@ build_depends:
   - build-essential
 architecture: any
 rules_dh_line: "dh $@"
-files: []
+files:
+  - path: hello.c
+    template: hello.c.tpl
+  - path: Makefile
+    template: Makefile.tpl
+  - path: debian/install
+    template: install.tpl
+    skeleton_only: true

data/templates/shell/install.tpl

@@ -0,0 +1 @@
+{command}.sh usr/bin/{command}

data/templates/shell/manifest.yml

@@ -2,7 +2,10 @@
 ## /usr/bin with plain `dh $@` plumbing. Detection is not marker-based: the
 ## single-script heuristic of src/new/detect.rs (a lone *.sh or shebang
 ## file) maps here. The probe pre-filling the wizard answers from the
-## script file name lives in src/new/templates/shell.rs.
+## script file name lives in src/new/templates/shell.rs; everything else
+## is the data below (the skeleton script is executable, the install
+## mapping exists for skeletons only — packaging an existing tree leaves
+## the mapping to the user).
 ##
 ## Schema: see src/new/templates/mod.rs.
 
@@ -13,4 +16,10 @@ detect:
 build_depends: []
 architecture: all
 rules_dh_line: "dh $@"
-files: []
+files:
+  - path: "{command}.sh"
+    template: script.tpl
+    executable: true
+  - path: debian/install
+    template: install.tpl
+    skeleton_only: true

data/templates/shell/script.tpl

@@ -0,0 +1,3 @@
+#!/bin/sh
+# Placeholder for {name}, generated by `pkh new`.
+echo "Hello from {command}!"