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/zerocopy/tests/ui/try_transmute.nightly.stderr

@@ -0,0 +1,124 @@
+error[E0277]: the trait bound `NotZerocopy: TryFromBytes` is not satisfied
+   --> $DIR/try_transmute.rs:15:33
+    |
+ 15 |     let dst_not_try_from_bytes: Result<NotZerocopy, _> = try_transmute!(AU16(0));
+    |                                 ^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
+    |
+help: the trait `TryFromBytes` is not implemented for `NotZerocopy`
+   --> $DIR/../include.rs:15:5
+    |
+ 15 |     pub struct NotZerocopy<T = ()>(pub T);
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    = note: Consider adding `#[derive(TryFromBytes)]` to `NotZerocopy`
+    = help: the following other types implement trait `TryFromBytes`:
+              ()
+              (A, B)
+              (A, B, C)
+              (A, B, C, D)
+              (A, B, C, D, E)
+              (A, B, C, D, E, F)
+              (A, B, C, D, E, F, G)
+              (A, B, C, D, E, F, G, H)
+            and 153 others
+note: required by a bound in `ValidityError`
+   --> src/error.rs:588:45
+    |
+588 | pub struct ValidityError<Src, Dst: ?Sized + TryFromBytes> {
+    |                                             ^^^^^^^^^^^^ required by this bound in `ValidityError`
+
+error[E0277]: the trait bound `NotZerocopy: TryFromBytes` is not satisfied
+   --> $DIR/try_transmute.rs:15:58
+    |
+ 15 |     let dst_not_try_from_bytes: Result<NotZerocopy, _> = try_transmute!(AU16(0));
+    |                                                          ^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
+    |
+help: the trait `TryFromBytes` is not implemented for `NotZerocopy`
+   --> $DIR/../include.rs:15:5
+    |
+ 15 |     pub struct NotZerocopy<T = ()>(pub T);
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    = note: Consider adding `#[derive(TryFromBytes)]` to `NotZerocopy`
+    = help: the following other types implement trait `TryFromBytes`:
+              ()
+              (A, B)
+              (A, B, C)
+              (A, B, C, D)
+              (A, B, C, D, E)
+              (A, B, C, D, E, F)
+              (A, B, C, D, E, F, G)
+              (A, B, C, D, E, F, G, H)
+            and 153 others
+note: required by a bound in `zerocopy::util::macro_util::try_transmute`
+   --> src/util/macro_util.rs:526:10
+    |
+523 | pub fn try_transmute<Src, Dst>(src: Src) -> Result<Dst, ValidityError<Src, Dst>>
+    |        ------------- required by a bound in this function
+...
+526 |     Dst: TryFromBytes,
+    |          ^^^^^^^^^^^^ required by this bound in `try_transmute`
+    = note: this error originates in the macro `try_transmute` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `NotZerocopy: TryFromBytes` is not satisfied
+   --> $DIR/try_transmute.rs:15:58
+    |
+ 15 |     let dst_not_try_from_bytes: Result<NotZerocopy, _> = try_transmute!(AU16(0));
+    |                                                          ^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
+    |
+help: the trait `TryFromBytes` is not implemented for `NotZerocopy`
+   --> $DIR/../include.rs:15:5
+    |
+ 15 |     pub struct NotZerocopy<T = ()>(pub T);
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    = note: Consider adding `#[derive(TryFromBytes)]` to `NotZerocopy`
+    = help: the following other types implement trait `TryFromBytes`:
+              ()
+              (A, B)
+              (A, B, C)
+              (A, B, C, D)
+              (A, B, C, D, E)
+              (A, B, C, D, E, F)
+              (A, B, C, D, E, F, G)
+              (A, B, C, D, E, F, G, H)
+            and 153 others
+note: required by a bound in `ValidityError`
+   --> src/error.rs:588:45
+    |
+588 | pub struct ValidityError<Src, Dst: ?Sized + TryFromBytes> {
+    |                                             ^^^^^^^^^^^^ required by this bound in `ValidityError`
+    = note: this error originates in the macro `try_transmute` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `NotZerocopy<AU16>: IntoBytes` is not satisfied
+   --> $DIR/try_transmute.rs:21:47
+    |
+ 21 |     let src_not_into_bytes: Result<AU16, _> = try_transmute!(NotZerocopy(AU16(0)));
+    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
+    |
+help: the trait `IntoBytes` is not implemented for `NotZerocopy<AU16>`
+   --> $DIR/../include.rs:15:5
+    |
+ 15 |     pub struct NotZerocopy<T = ()>(pub T);
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    = note: Consider adding `#[derive(IntoBytes)]` to `NotZerocopy<AU16>`
+    = help: the following other types implement trait `IntoBytes`:
+              ()
+              AU16
+              AtomicBool
+              AtomicI16
+              AtomicI32
+              AtomicI64
+              AtomicI8
+              AtomicIsize
+            and 68 others
+note: required by a bound in `zerocopy::util::macro_util::try_transmute`
+   --> src/util/macro_util.rs:525:10
+    |
+523 | pub fn try_transmute<Src, Dst>(src: Src) -> Result<Dst, ValidityError<Src, Dst>>
+    |        ------------- required by a bound in this function
+524 | where
+525 |     Src: IntoBytes,
+    |          ^^^^^^^^^ required by this bound in `try_transmute`
+    = note: this error originates in the macro `try_transmute` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0277`.