Initial travler-rotor library scaffolding

Extract Gabe Emerson's Trav'ler rotor scripts into a proper Python
library with firmware protocol abstraction (HAL 2.05 + HAL 0.0.00),
Hamlib rotctld TCP server, Click CLI, and isolated leap-frog algorithm
with the elevation copy-paste bug fixed.

docs/bugs.md

@@ -0,0 +1,41 @@
+# Known Bugs in Original Code
+
+## Leap-Frog Elevation Bug
+
+**Location:** `Trav-ler-Rotor-For-HAL-2.05/travler_rotor.py` lines 98-105
+
+**Issue:** The elevation delta section of the leap-frog algorithm modifies
+`target_az` instead of `target_el`. This is a copy-paste error from the
+azimuth section above it.
+
+**Original code (lines 90-105):**
+```python
+# Azimuth compensation (correct)
+if target_az - current_az > 2:
+    target_az+=1
+elif target_az - current_az < -2:
+    target_az-=1
+elif target_az - current_az > 1:
+    target_az+=0.5
+elif target_az - current_az < -1:
+    target_az-=0.5
+
+# Elevation compensation (BUG: modifies target_az instead of target_el)
+if target_el - current_el > 2:
+    target_az+=1              # <-- should be target_el
+elif target_el - current_el < -2:
+    target_az-=1              # <-- should be target_el
+elif target_el - current_el > 1:
+    target_az+=0.5            # <-- should be target_el
+elif target_el - current_el < -1:
+    target_az-=0.5            # <-- should be target_el
+```
+
+**Impact:**
+- Elevation leap-frog compensation was never applied, so the dish would
+  lag behind in elevation during fast satellite passes
+- Azimuth received double compensation (its own delta + the elevation delta),
+  causing over-correction on the azimuth axis
+
+**Fix:** In `travler_rotor.leapfrog.apply_leapfrog()`, the elevation
+compensation correctly modifies `target_el`.