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/paste/tests/ui/case-warning.rs

@@ -0,0 +1,15 @@
+#![deny(warnings)]
+
+use paste::paste;
+
+macro_rules! m {
+    ($i:ident) => {
+        paste! {
+            pub fn [<foo $i>]() {}
+        }
+    };
+}
+
+m!(Bar);
+
+fn main() {}

vendor/paste/tests/ui/case-warning.stderr

@@ -0,0 +1,16 @@
+error: function `fooBar` should have a snake case name
+  --> tests/ui/case-warning.rs:8:20
+   |
+8  |             pub fn [<foo $i>]() {}
+   |                    ^^^^^^^^^^ help: convert the identifier to snake case: `foo_bar`
+...
+13 | m!(Bar);
+   | ------- in this macro invocation
+   |
+note: the lint level is defined here
+  --> tests/ui/case-warning.rs:1:9
+   |
+1  | #![deny(warnings)]
+   |         ^^^^^^^^
+   = note: `#[deny(non_snake_case)]` implied by `#[deny(warnings)]`
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)

vendor/paste/tests/ui/env-empty.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<env!()>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/env-empty.stderr

@@ -0,0 +1,5 @@
+error: expected string literal as argument to env! macro
+ --> tests/ui/env-empty.rs:4:10
+  |
+4 |     fn [<env!()>]() {}
+  |          ^^^^^^

vendor/paste/tests/ui/env-non-string.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<env!(1.31)>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/env-non-string.stderr

@@ -0,0 +1,5 @@
+error: expected string literal
+ --> tests/ui/env-non-string.rs:4:15
+  |
+4 |     fn [<env!(1.31)>]() {}
+  |               ^^^^

vendor/paste/tests/ui/env-suffix.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<env!("VAR"suffix)>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/env-suffix.stderr

@@ -0,0 +1,5 @@
+error: expected string literal
+ --> tests/ui/env-suffix.rs:4:15
+  |
+4 |     fn [<env!("VAR"suffix)>]() {}
+  |               ^^^^^^^^^^^

vendor/paste/tests/ui/env-unexpected.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<env!("VAR" "VAR")>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/env-unexpected.stderr

@@ -0,0 +1,5 @@
+error: unexpected token in env! macro
+ --> tests/ui/env-unexpected.rs:4:21
+  |
+4 |     fn [<env!("VAR" "VAR")>]() {}
+  |                     ^^^^^

vendor/paste/tests/ui/invalid-ident.rs

@@ -0,0 +1,15 @@
+use paste::paste;
+
+paste! {
+    fn [<0 f>]() {}
+}
+
+paste! {
+    fn [<f '"'>]() {}
+}
+
+paste! {
+    fn [<f "'">]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/invalid-ident.stderr

@@ -0,0 +1,26 @@
+error: expected identifier, found `0f`
+ --> tests/ui/invalid-ident.rs:3:1
+  |
+3 | / paste! {
+4 | |     fn [<0 f>]() {}
+5 | | }
+  | |_^ expected identifier
+  |
+help: identifiers cannot start with a number
+ --> tests/ui/invalid-ident.rs:3:1
+  |
+3 | paste! {
+  | ^
+  = note: this error originates in the macro `paste` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `"f\""` is not a valid identifier
+ --> tests/ui/invalid-ident.rs:8:8
+  |
+8 |     fn [<f '"'>]() {}
+  |        ^^^^^^^^^
+
+error: `"f'"` is not a valid identifier
+  --> tests/ui/invalid-ident.rs:12:8
+   |
+12 |     fn [<f "'">]() {}
+   |        ^^^^^^^^^

vendor/paste/tests/ui/missing-paren-on-env.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<env! huh>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/missing-paren-on-env.stderr

@@ -0,0 +1,5 @@
+error: expected `(`
+ --> tests/ui/missing-paren-on-env.rs:4:15
+  |
+4 |     fn [<env! huh>]() {}
+  |               ^^^

vendor/paste/tests/ui/no-env-var.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<a env!("PASTE_UNKNOWN") b>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/no-env-var.stderr

@@ -0,0 +1,5 @@
+error: no such env var: "PASTE_UNKNOWN"
+ --> tests/ui/no-env-var.rs:4:17
+  |
+4 |     fn [<a env!("PASTE_UNKNOWN") b>]() {}
+  |                 ^^^^^^^^^^^^^^^

vendor/paste/tests/ui/no-ident-after-colon.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<name:0>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/no-ident-after-colon.stderr

@@ -0,0 +1,5 @@
+error: expected identifier after `:`
+ --> tests/ui/no-ident-after-colon.rs:4:15
+  |
+4 |     fn [<name:0>]() {}
+  |               ^

vendor/paste/tests/ui/unexpected-group.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<a {} b>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/unexpected-group.stderr

@@ -0,0 +1,5 @@
+error: unexpected token
+ --> tests/ui/unexpected-group.rs:4:12
+  |
+4 |     fn [<a {} b>]() {}
+  |            ^^

vendor/paste/tests/ui/unexpected-modifier.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<:lower x>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/unexpected-modifier.stderr

@@ -0,0 +1,5 @@
+error: unexpected modifier
+ --> tests/ui/unexpected-modifier.rs:4:10
+  |
+4 |     fn [<:lower x>]() {}
+  |          ^^^^^^

vendor/paste/tests/ui/unexpected-punct.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<a + b>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/unexpected-punct.stderr

@@ -0,0 +1,5 @@
+error: unexpected punct
+ --> tests/ui/unexpected-punct.rs:4:12
+  |
+4 |     fn [<a + b>]() {}
+  |            ^

vendor/paste/tests/ui/unsupported-literal.rs

@@ -0,0 +1,21 @@
+use paste::paste;
+
+paste! {
+    fn [<x 1e+100 z>]() {}
+}
+
+paste! {
+    // `xyz` is not correct. `xbyz` is certainly not correct. Maybe `x121z`
+    // would be justifiable but for now don't accept this.
+    fn [<x b'y' z>]() {}
+}
+
+paste! {
+    fn [<x b"y" z>]() {}
+}
+
+paste! {
+    fn [<x br"y" z>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/unsupported-literal.stderr

@@ -0,0 +1,23 @@
+error: unsupported literal
+ --> tests/ui/unsupported-literal.rs:4:12
+  |
+4 |     fn [<x 1e+100 z>]() {}
+  |            ^^^^^^
+
+error: unsupported literal
+  --> tests/ui/unsupported-literal.rs:10:12
+   |
+10 |     fn [<x b'y' z>]() {}
+   |            ^^^^
+
+error: unsupported literal
+  --> tests/ui/unsupported-literal.rs:14:12
+   |
+14 |     fn [<x b"y" z>]() {}
+   |            ^^^^
+
+error: unsupported literal
+  --> tests/ui/unsupported-literal.rs:18:12
+   |
+18 |     fn [<x br"y" z>]() {}
+   |            ^^^^^

vendor/paste/tests/ui/unsupported-modifier.rs

@@ -0,0 +1,7 @@
+use paste::paste;
+
+paste! {
+    fn [<a:pillow>]() {}
+}
+
+fn main() {}

vendor/paste/tests/ui/unsupported-modifier.stderr

@@ -0,0 +1,5 @@
+error: unsupported modifier
+ --> tests/ui/unsupported-modifier.rs:4:11
+  |
+4 |     fn [<a:pillow>]() {}
+  |           ^^^^^^^