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/benches/read_from_bytes.x86-64.mca

@@ -0,0 +1,65 @@
+Iterations:        100
+Instructions:      1300
+Total Cycles:      377
+Total uOps:        1400
+
+Dispatch Width:    4
+uOps Per Cycle:    3.71
+IPC:               3.45
+Block RThroughput: 3.5
+
+
+Instruction Info:
+[1]: #uOps
+[2]: Latency
+[3]: RThroughput
+[4]: MayLoad
+[5]: MayStore
+[6]: HasSideEffects (U)
+
+[1]    [2]    [3]    [4]    [5]    [6]    Instructions:
+ 1      1     0.33                        mov	rcx, rsi
+ 1      1     0.33                        cmp	rsi, 6
+ 1      1     1.00                        jne	.LBB5_2
+ 1      5     0.50    *                   mov	eax, dword ptr [rdi]
+ 1      5     0.50    *                   movzx	ecx, word ptr [rdi + 4]
+ 1      1     0.50                        shl	rcx, 32
+ 1      1     0.33                        or	rcx, rax
+ 1      1     0.50                        shl	rcx, 16
+ 1      1     0.33                        inc	rcx
+ 1      0     0.25                        xor	eax, eax
+ 1      1     0.33                        cmp	rsi, 6
+ 2      2     0.67                        cmove	rax, rcx
+ 1      1     1.00                  U     ret
+
+
+Resources:
+[0]   - SBDivider
+[1]   - SBFPDivider
+[2]   - SBPort0
+[3]   - SBPort1
+[4]   - SBPort4
+[5]   - SBPort5
+[6.0] - SBPort23
+[6.1] - SBPort23
+
+
+Resource pressure per iteration:
+[0]    [1]    [2]    [3]    [4]    [5]    [6.0]  [6.1]  
+ -      -     3.66   3.67    -     3.67   1.00   1.00   
+
+Resource pressure by instruction:
+[0]    [1]    [2]    [3]    [4]    [5]    [6.0]  [6.1]  Instructions:
+ -      -     0.63   0.36    -     0.01    -      -     mov	rcx, rsi
+ -      -     0.05   0.05    -     0.90    -      -     cmp	rsi, 6
+ -      -      -      -      -     1.00    -      -     jne	.LBB5_2
+ -      -      -      -      -      -      -     1.00   mov	eax, dword ptr [rdi]
+ -      -      -      -      -      -     1.00    -     movzx	ecx, word ptr [rdi + 4]
+ -      -     0.97    -      -     0.03    -      -     shl	rcx, 32
+ -      -     0.02   0.35    -     0.63    -      -     or	rcx, rax
+ -      -     0.98    -      -     0.02    -      -     shl	rcx, 16
+ -      -      -     0.98    -     0.02    -      -     inc	rcx
+ -      -      -      -      -      -      -      -     xor	eax, eax
+ -      -     0.03   0.93    -     0.04    -      -     cmp	rsi, 6
+ -      -     0.98   1.00    -     0.02    -      -     cmove	rax, rcx
+ -      -      -      -      -     1.00    -      -     ret