feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/defmt-macros/src/lib.rs

@@ -0,0 +1,209 @@
+//! INTERNAL; DO NOT USE. Please use the `defmt` crate to access the functionality implemented here
+
+#![doc(html_logo_url = "https://knurling.ferrous-systems.com/knurling_logo_light_text.svg")]
+
+use defmt_parser::Level;
+use proc_macro::TokenStream;
+use proc_macro2::TokenStream as TokenStream2;
+use proc_macro_error2::proc_macro_error;
+use quote::quote;
+
+mod attributes;
+mod cargo;
+mod construct;
+mod consts;
+mod derives;
+mod function_like;
+mod items;
+
+// NOTE some proc-macro functions have an `_` (underscore) suffix. This is intentional.
+// If left unsuffixed the procedural macros would shadow macros defined in `std` (like `assert`)
+// within the context of this entire crate, which leads to lots of confusion.
+
+/* # Attributes */
+#[proc_macro_attribute]
+#[proc_macro_error]
+pub fn global_logger(args: TokenStream, item: TokenStream) -> TokenStream {
+    attributes::global_logger::expand(args, item)
+}
+
+#[proc_macro_attribute]
+#[proc_macro_error]
+pub fn panic_handler(args: TokenStream, item: TokenStream) -> TokenStream {
+    attributes::panic_handler::expand(args, item)
+}
+
+/* # Derives */
+#[proc_macro_derive(Format, attributes(defmt))]
+#[proc_macro_error]
+pub fn format(input: TokenStream) -> TokenStream {
+    derives::format::expand(input)
+}
+
+/* # Function-like */
+#[proc_macro]
+#[proc_macro_error]
+pub fn assert_(args: TokenStream) -> TokenStream {
+    function_like::assert_like::assert::expand(args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn assert_eq_(args: TokenStream) -> TokenStream {
+    function_like::assert_binop::eq(args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn assert_ne_(args: TokenStream) -> TokenStream {
+    function_like::assert_binop::ne(args)
+}
+
+/* ## `debug_` variants */
+// NOTE these `debug_*` macros can be written using `macro_rules!` (that'd be simpler) but that
+// results in an incorrect source code location being reported: the location of the `macro_rules!`
+// statement is reported. Using a proc-macro results in the call site being reported, which is what
+// we want
+#[proc_macro]
+#[proc_macro_error]
+pub fn debug_assert_(input: TokenStream) -> TokenStream {
+    let assert = TokenStream2::from(assert_(input));
+    quote!(if cfg!(debug_assertions) {
+        #assert
+    })
+    .into()
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn debug_assert_eq_(input: TokenStream) -> TokenStream {
+    let assert = TokenStream2::from(assert_eq_(input));
+    quote!(if cfg!(debug_assertions) {
+        #assert
+    })
+    .into()
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn debug_assert_ne_(input: TokenStream) -> TokenStream {
+    let assert = TokenStream2::from(assert_ne_(input));
+    quote!(if cfg!(debug_assertions) {
+        #assert
+    })
+    .into()
+}
+/* ## end of `debug_` variants */
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn dbg(args: TokenStream) -> TokenStream {
+    function_like::dbg::expand(args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn intern(args: TokenStream) -> TokenStream {
+    function_like::intern::expand(args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn internp(args: TokenStream) -> TokenStream {
+    function_like::internp::expand(args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn println(args: TokenStream) -> TokenStream {
+    function_like::println::expand(args)
+}
+
+/* ## Logging macros */
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn trace(args: TokenStream) -> TokenStream {
+    function_like::log::expand(Level::Trace, args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn debug(args: TokenStream) -> TokenStream {
+    function_like::log::expand(Level::Debug, args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn info(args: TokenStream) -> TokenStream {
+    function_like::log::expand(Level::Info, args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn warn(args: TokenStream) -> TokenStream {
+    function_like::log::expand(Level::Warn, args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn error(args: TokenStream) -> TokenStream {
+    function_like::log::expand(Level::Error, args)
+}
+/* ## end of logging macros */
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn panic_(args: TokenStream) -> TokenStream {
+    function_like::panic_like::expand(args, "panicked at 'explicit panic'", |format_string| {
+        format!("panicked at '{format_string}'")
+    })
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn todo_(args: TokenStream) -> TokenStream {
+    function_like::panic_like::expand(args, "panicked at 'not yet implemented'", |format_string| {
+        format!("panicked at 'not yet implemented: {format_string}'")
+    })
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn unreachable_(args: TokenStream) -> TokenStream {
+    function_like::panic_like::expand(
+        args,
+        "panicked at 'internal error: entered unreachable code'",
+        |format_string| {
+            format!(
+                "panicked at 'internal error: entered unreachable code: {}'",
+                format_string
+            )
+        },
+    )
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn unwrap(args: TokenStream) -> TokenStream {
+    function_like::assert_like::unwrap::expand(args)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn write(args: TokenStream) -> TokenStream {
+    function_like::write::expand(args)
+}
+
+/* # Items */
+#[proc_macro]
+#[proc_macro_error]
+pub fn bitflags(ts: TokenStream) -> TokenStream {
+    items::bitflags::expand(ts)
+}
+
+#[proc_macro]
+#[proc_macro_error]
+pub fn timestamp(args: TokenStream) -> TokenStream {
+    items::timestamp::expand(args)
+}