Add session summary for camera zoom and UI cleanup improvements

docs/session_summaries/2026-01-30-camera-zoom-and-ui-cleanup.md

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+# 2026-01-30 Camera Zoom and UI Cleanup
+
+## Changes Made
+
+### Camera System Improvements
+- Extracted hardcoded camera control values to #define constants (CAMERA_ORBIT_ANGLE_SPEED, CAMERA_ZOOM_DELTA, CAMERA_MIN_DISTANCE, etc.)
+- Implemented dynamic camera zoom with percentage-based speed (7% of current distance per keypress)
+- Added delta clamping (ZOOM_MIN_DELTA 0.05, ZOOM_MAX_DELTA 5.0f) to prevent too-slow or too-fast zooming
+- Fixed camera culling by accounting for raylib's near cull plane (0.05) in minimum distance calculation
+- Camera minimum distance now uses max(average_children_distance, body_radius * 100) when children exist
+- Camera minimum distance uses body_radius * 100 when no children exist (prevents clipping for bodies like Sun)
+
+### Camera Targeting Simplification
+- Removed `selected_craft_index` from RenderState struct - camera now only tracks bodies
+- Moved spacecraft selection tracking to UIState struct (`selected_craft_index` field)
+- Camera now always focuses on bodies (directly selected or parent of selected spacecraft)
+- Eliminated ~30 lines of duplicate/special-case code from renderer module
+- All renderer functions now use single body-focused code path
+
+### Bug Fixes
+- Fixed camera distance when switching from Sun (large radius) to Earth (small radius) - camera no longer clips inside Earth
+- Fixed spacecraft panel showing for 1 frame then disappearing - `ui_state.selected_craft_index` now persists across frames instead of being reset
+
+## Commits
+1. Extract camera control constants to #define macros
+2. Implement dynamic camera zoom with percentage-based speed and distance clamping
+3. Fix camera culling by accounting for near cull plane in minimum distance calculation
+4. Simplify camera targeting by removing spacecraft selection from renderer
+5. Fix camera distance to account for body size when switching targets
+6. Fix spacecraft panel showing for 1 frame then disappearing
+
+## Results
+- **Net line count:** -56 lines (44 insertions, 100 deletions)
+- **Files modified:** 5 (src/renderer.cpp, src/renderer.h, src/ui_renderer.cpp, src/ui_renderer.h, src/main.cpp)
+- **Build status:** Successful, no errors
+- **Test status:** Camera zoom and minimum distance verified, spacecraft panel persistence confirmed
+
+## Next Steps
+- Consider extracting remaining hardcoded rendering constants (grid parameters, spacecraft rendering, maneuver markers, orbit rendering, child indicators)
+- Consider using parent's SOI radius instead of radius for more physically meaningful minimum distances