deps: remove derive_more and heck (#17)

## Description

`derive_more` is not needed for the single place where it was used, and
`heck` was unused.

## Breaking Changes

<!-- Optional, if there are any breaking changes document them,
including how to migrate older code. -->

## Notes & open questions

<!-- Any notes, remarks or open questions you have to make about the PR.
-->

## Change checklist

- [x] Self-review.
- [x] Documentation updates following the [style
guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text),
if relevant.
- [x] Tests if relevant.
- [x] All breaking changes documented.

Author: Frando

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "n0-error"
-version = "0.1.0"
+version = "0.1.1"
 edition = "2024"
 readme = "README.md"
 description = "ergonomic errors with call-site location"
@@ -11,7 +11,6 @@ keywords = ["error", "location", "ergonomic"]
 
 [dependencies]
 anyhow = { version = "1.0.100", optional = true }
-derive_more = { version = "2.0.1", features = ["debug", "display"] }
 n0-error-macros = { path = "n0-error-macros", version = "0.1.0" }
 spez = "0.1.2"
 

Cargo.toml

@@ -12,7 +12,6 @@ keywords = ["error", "location", "ergonomic"]
 proc-macro = true
 
 [dependencies]
-heck = "0.5"
 proc-macro2 = "1"
 quote = "1"
 syn = { version = "2", features = ["full", "extra-traits"] }

n0-error-macros/Cargo.toml

@@ -1,10 +1,21 @@
 use std::{fmt, sync::OnceLock};
 
 /// Wrapper around `std::panic::Location` used for display in reports.
-#[derive(derive_more::Debug, derive_more::Display, Clone, Copy)]
-#[debug("{_0:?}")]
+#[derive(Clone, Copy)]
 pub struct Location(&'static std::panic::Location<'static>);
 
+impl fmt::Display for Location {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self.0, f)
+    }
+}
+
+impl fmt::Debug for Location {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self.0, f)
+    }
+}
+
 /// Captured metadata for an error creation site.
 ///
 /// Currently this only contains the call-site [`Location`].