refactor!: replace build.rs with compile-time macro build steps

BREAKING CHANGE: Replace the `build`/`builds` feature system with
compile-time macro-driven generation. `gen_program!()` now automatically
invokes `build_comp!()` and `build_pathf!()` when the `comp`/`pathf`
features are enabled, eliminating the need for `build.rs` and
`[build-dependencies]` blocks.

This removes the `build` feature, the `mingling::build` module, and all
related build-time API functions. Completion scripts are now written to
`{target_directory}/mingling/` instead of `target/release/`. The
`mingling_cli` uses `build_comp!("mling")` for its custom binary name.

3 files changed, 11 insertions, 16 deletions

diff --git a/.run/src/bin/install-mling.ps1 b/.run/src/bin/install-mling.ps1
index 2bc28ee..2b55a09 100644
--- a/.run/src/bin/install-mling.ps1
+++ b/.run/src/bin/install-mling.ps1
@@ -6,5 +6,5 @@ New-Item -ItemType Directory -Force -Path .temp/mling/bin, .temp/mling/scripts |
 
 Copy-Item .temp/target/release/mling.exe .temp/mling/bin/
 Copy-Item .temp/target/release/mingling-cli.exe .temp/mling/bin/
-Copy-Item .temp/target/release/mling_comp.ps1 .temp/mling/scripts/mling_comp.ps1
+Copy-Item .temp/target/mingling/mling_comp.ps1 .temp/mling/scripts/mling_comp.ps1
 Copy-Item mingling_cli/scripts/load_mling.ps1 .temp/mling/
diff --git a/.run/src/bin/install-mling.sh b/.run/src/bin/install-mling.sh
index 139e221..e8cfa18 100755
--- a/.run/src/bin/install-mling.sh
+++ b/.run/src/bin/install-mling.sh
@@ -10,7 +10,7 @@ cp .temp/target/release/mling .temp/mling/bin/
 cp .temp/target/release/mingling-cli .temp/mling/bin/
 
 for comp in zsh sh fish; do
-    cp ".temp/target/release/mling_comp.$comp" ".temp/mling/scripts/mling_comp.$comp"
+    cp ".temp/target/mingling/mling_comp.$comp" ".temp/mling/scripts/mling_comp.$comp"
 done
 cp mingling_cli/scripts/load_mling.zsh .temp/mling/
 cp mingling_cli/scripts/load_mling.sh .temp/mling/
diff --git a/.run/src/verify.rs b/.run/src/verify.rs
index 0a4b354..b79bb73 100644
--- a/.run/src/verify.rs
+++ b/.run/src/verify.rs
@@ -215,16 +215,15 @@ pub fn generate_cargo_toml(block: &CodeBlock, package_name: &str, manifest_path:
         )
     };
 
-    // Build-time blocks: add `builds` by default, merge with explicit features
+    // Build-time blocks: mirror the declared features into [build-dependencies]
+    // so that build.rs can use the same feature set as the crate itself.
     let build_deps_section = if block.is_build_time {
-        let mut all_feats = vec!["builds".to_string()];
-        for f in &block.features {
-            if f != "builds" {
-                all_feats.push(f.clone());
-            }
-        }
-        let feats_str: Vec<String> = all_feats.iter().map(|f| format!("\"{f}\"")).collect();
-        let build_feats = format!("features = [{}]", feats_str.join(", "));
+        let feats_str: Vec<String> = block.features.iter().map(|f| format!("\"{f}\"")).collect();
+        let build_feats = if feats_str.is_empty() {
+            String::new()
+        } else {
+            format!("features = [{}]", feats_str.join(", "))
+        };
         format!(
             "\n[build-dependencies]\nmingling = {{ path = \"{mingling_path}\", {build_feats} }}\n"
         )
@@ -292,14 +291,10 @@ pub fn generate_main_rs(block: &CodeBlock) -> String {
 
 /// Generate build.rs for a build-time block
 ///
-/// Default: `use mingling::builds::*;`, code wrapped in `fn main() { }`.
+/// Default: code wrapped in `fn main() { }`.
 pub fn generate_build_rs(block: &CodeBlock) -> String {
     let mut output = String::from("#![allow(dead_code)]\n#![allow(unused)]\n");
 
-    if !block.code.contains("use mingling::build::*;") {
-        output.push_str("#[allow(unused_imports)]\nuse mingling::build::*;\n\n");
-    }
-
     if block.has_main {
         output.push_str(&block.code);
     } else {