refactor(core): improve code style and public API clarity

Replace bool-based settings with enums, refine visibility and
signatures, and standardize `Self` usage across the crate.

- Introduce `ErrorOutput`, `RenderOutput`, `PanicSilence`, `Verbosity`,
  `ColorOutput`, and `ProgressOutput` enums for clearer configuration
  semantics
- Make `GlobalResources`, `ProgramCell`, and
  `split_input`/`split_input_string` public
- Change hook info parameters to accept references and
  `split_input_string` to take `&str`
- Apply `Self` shorthand throughout implementations and add
  `#[must_use]` attributes where appropriate
- Enable strict clippy lints with targeted allowances

4 files changed, 31 insertions, 27 deletions

diff --git a/mingling_core/src/comp/comp_ctx.rs b/mingling_core/src/comp/comp_ctx.rs
index 8d7fa5c..6384909 100644
--- a/mingling_core/src/comp/comp_ctx.rs
+++ b/mingling_core/src/comp/comp_ctx.rs
@@ -10,6 +10,7 @@ where
     /// (defined by [`COMPLETION_SUBCOMMAND`]) appears among the parsed arguments.
     /// When `true`, the program should generate shell completions instead of
     /// running its normal execution path.
+    #[must_use]
     pub fn is_completing(&self) -> bool {
         // Check if the first argument (args[1]) is the completion subcommand
         self.args
diff --git a/mingling_core/src/comp/flags.rs b/mingling_core/src/comp/flags.rs
index 8aecf1b..0867122 100644
--- a/mingling_core/src/comp/flags.rs
+++ b/mingling_core/src/comp/flags.rs
@@ -23,11 +23,11 @@ pub enum ShellFlag {
 impl From<String> for ShellFlag {
     fn from(s: String) -> Self {
         match s.trim().to_lowercase().as_str() {
-            "zsh" => ShellFlag::Zsh,
-            "bash" => ShellFlag::Bash,
-            "fish" => ShellFlag::Fish,
-            "pwsh" | "ps1" | "powershell" => ShellFlag::Powershell,
-            other => ShellFlag::Other(snake_case!(other)),
+            "zsh" => Self::Zsh,
+            "bash" => Self::Bash,
+            "fish" => Self::Fish,
+            "pwsh" | "ps1" | "powershell" => Self::Powershell,
+            other => Self::Other(snake_case!(other)),
         }
     }
 }
diff --git a/mingling_core/src/comp/shell_ctx.rs b/mingling_core/src/comp/shell_ctx.rs
index 734b5d2..ceb433f 100644
--- a/mingling_core/src/comp/shell_ctx.rs
+++ b/mingling_core/src/comp/shell_ctx.rs
@@ -64,7 +64,7 @@ impl TryFrom<Vec<String>> for ShellContext {
             .map(|s| s.replace('^', "-"))
             .collect();
 
-        Ok(ShellContext {
+        Ok(Self {
             command_line: command_line.replace('^', "-"),
             cursor_position,
             current_word: current_word.replace('^', "-"),
@@ -201,7 +201,7 @@ impl ShellContext {
         }
         #[cfg(not(target_os = "windows"))]
         {
-            self.current_word.starts_with("-")
+            self.current_word.starts_with('-')
         }
     }
 
diff --git a/mingling_core/src/comp/suggest.rs b/mingling_core/src/comp/suggest.rs
index 804d622..27b227f 100644
--- a/mingling_core/src/comp/suggest.rs
+++ b/mingling_core/src/comp/suggest.rs
@@ -18,15 +18,15 @@ pub enum Suggest {
 }
 
 impl Suggest {
-    /// Creates a new Suggest variant containing a `BTreeSet` of suggestions.
+    /// Creates a new `Suggest` variant containing an empty `BTreeSet` of suggestions.
     #[must_use]
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self::Suggest(BTreeSet::new())
     }
 
     /// Creates a `FileCompletion` variant.
     #[must_use]
-    pub fn file_comp() -> Self {
+    pub const fn file_comp() -> Self {
         Self::FileCompletion
     }
 
@@ -47,11 +47,12 @@ impl Suggest {
     /// If both values are `Suggest::Suggest`, their `BTreeSet`s are merged
     /// (all items from `other` are added into `self`). Otherwise, the first
     /// `Suggest::Suggest` (or `FileCompletion`) is returned unchanged.
-    pub fn combine(self, other: impl Into<Suggest>) -> Self {
+    #[must_use]
+    pub fn combine(self, other: impl Into<Self>) -> Self {
         let other = other.into();
         match (self, other) {
-            (Suggest::Suggest(suggest), Suggest::Suggest(other)) => {
-                Suggest::Suggest(suggest.into_iter().chain(other).collect())
+            (Self::Suggest(suggest), Self::Suggest(other)) => {
+                Self::Suggest(suggest.into_iter().chain(other).collect())
             }
             (suggest, _) => suggest,
         }
@@ -109,10 +110,11 @@ impl Suggest {
     /// A new `Suggest` value where each item's suggestion text is prefixed
     /// with the given string. For example, `["foo", "bar"]` with prefix `"--"`
     /// becomes `["--foo", "--bar"]`.
-    pub fn add_prefix(self, prefix: impl Into<String>) -> Suggest {
+    #[must_use]
+    pub fn add_prefix(self, prefix: impl Into<String>) -> Self {
         let suggest = match self {
-            Suggest::Suggest(s) => s,
-            Suggest::FileCompletion => return Suggest::FileCompletion,
+            Self::Suggest(s) => s,
+            Self::FileCompletion => return Self::FileCompletion,
         };
         let prefix = prefix.into();
         let prefixed = suggest
@@ -123,7 +125,7 @@ impl Suggest {
                 new_item
             })
             .collect();
-        Suggest::Suggest(prefixed)
+        Self::Suggest(prefixed)
     }
 
     /// Appends a suffix to every suggestion in the `Suggest` set.
@@ -142,10 +144,11 @@ impl Suggest {
     /// A new `Suggest` value where each item's suggestion text is suffixed
     /// with the given string. For example, `["foo", "bar"]` with suffix `"="`
     /// becomes `["foo=", "bar="]`.
-    pub fn add_suffix(self, suffix: impl Into<String>) -> Suggest {
+    #[must_use]
+    pub fn add_suffix(self, suffix: impl Into<String>) -> Self {
         let suggest = match self {
-            Suggest::Suggest(s) => s,
-            Suggest::FileCompletion => return Suggest::FileCompletion,
+            Self::Suggest(s) => s,
+            Self::FileCompletion => return Self::FileCompletion,
         };
         let suffix = suffix.into();
         let suffixed = suggest
@@ -156,7 +159,7 @@ impl Suggest {
                 new_item
             })
             .collect();
-        Suggest::Suggest(suffixed)
+        Self::Suggest(suffixed)
     }
 }
 
@@ -170,7 +173,7 @@ where
             .into_iter()
             .map(|item| SuggestItem::new(item.into()))
             .collect();
-        Suggest::Suggest(suggests)
+        Self::Suggest(suggests)
     }
 }
 
@@ -213,7 +216,7 @@ pub enum SuggestItem {
 
 impl Default for SuggestItem {
     fn default() -> Self {
-        SuggestItem::Simple(String::new())
+        Self::Simple(String::new())
     }
 }
 
@@ -232,13 +235,13 @@ impl Ord for SuggestItem {
 impl SuggestItem {
     /// Creates a new simple suggestion without description.
     #[must_use]
-    pub fn new(suggest: String) -> Self {
+    pub const fn new(suggest: String) -> Self {
         Self::Simple(suggest)
     }
 
     /// Creates a new suggestion with a description.
     #[must_use]
-    pub fn new_with_desc(suggest: String, description: String) -> Self {
+    pub const fn new_with_desc(suggest: String, description: String) -> Self {
         Self::WithDescription(suggest, description)
     }
 
@@ -254,7 +257,7 @@ impl SuggestItem {
 
     /// Returns the suggestion text.
     #[must_use]
-    pub fn suggest(&self) -> &String {
+    pub const fn suggest(&self) -> &String {
         match self {
             Self::Simple(suggest) | Self::WithDescription(suggest, _) => suggest,
         }
@@ -269,7 +272,7 @@ impl SuggestItem {
 
     /// Returns the description if present.
     #[must_use]
-    pub fn description(&self) -> Option<&String> {
+    pub const fn description(&self) -> Option<&String> {
         match self {
             Self::Simple(_) => None,
             Self::WithDescription(_, description) => Some(description),