feat: add initial project scaffolding with Makefile, C sources, web UI, and documentation

Add Makefile with build targets for sudoku solver, generator, and coverage reporting.
Include NOTES.md explaining sudoku difficulty factors and solving techniques.
Add README.md with puzzle examples and generator output.
Implement app.js with Grid and Grid2 classes for rendering puzzle data in the browser.
Add box.c with functions for box indexing, grid-to-array conversion, and box value extraction.
Include footer.h with terminal size detection, cursor positioning, and footer display utilities.
Add index.html with CSS grid layout and script loading for the web interface.
Include rlib.h as a large utility header library.

sudoku_n/sudoku_header.h

@@ -0,0 +1,92 @@
+#ifndef SUDOKU_HEADER_H
+#define SUDOKU_HEADER_H
+#include "rlib.h"
+#include <stdlib.h>
+#include <stdio.h>
+typedef struct field_t {
+	unsigned int value;
+	unsigned int selected;
+	unsigned int initial;
+	unsigned int column;
+	unsigned int row;
+	unsigned int index;
+	unsigned char box;
+} field_t;
+
+field_t * new_field(){
+	field_t * field = (field_t *)calloc(1,sizeof(field_t));
+	return field;
+}
+
+typedef struct row_t {
+	unsigned int index;
+	field_t * columns;
+	unsigned int column_count;
+} row_t; 
+
+row_t * new_row(unsigned int size) {
+	row_t * row = (row_t *)calloc(sizeof(row_t),1);
+	row->columns = calloc(size,sizeof(field_t));
+	row->index = 0;
+	return row;
+}
+
+typedef struct grid_t {
+	unsigned int size;
+	unsigned int row_count;
+	unsigned int field_count;
+	row_t * rows;
+	field_t * fields;
+	field_t * (*get)(struct grid_t * grid, unsigned int row, unsigned int col);
+	field_t * (*get_empty_field)(struct grid_t * grid);
+} grid_t;
+
+field_t * grid_get(grid_t * grid, unsigned int row, unsigned int col){
+	return &grid->rows[row].columns[col];
+}
+field_t * grid_get_empty_field(grid_t *  grid){
+	for(uint i = 0; i < grid->size * grid->size; i++){
+		if(grid->fields[i].value == 0)
+			return &grid->fields[i];
+	}
+	return NULL;
+}
+/*
+char get_box_letter(grid_t * grid, unsigned int row, unsigned int col){
+	//char box_letter = 65 + (row)*grid->size / grid->size / 3 + row;  // (row*grid->size+col)+(grid->size / 3);// + grid->size % (grid->size / 3));
+	char box_letter = 65 + ((row % (grid->size / 3))) + grid->size % (grid->size / 3);// (row-1)*grid->size+(col-1)+(row-1)+(col-1); 
+		//(65 + row * (grid->size / 3) % (grid->size / 3)+col);  /// (grid->size / 3));
+	return box_letter;
+}*/
+
+
+grid_t * new_grid(unsigned int size){
+	grid_t * grid = (grid_t *)calloc(1,sizeof(grid_t));
+	grid->get = grid_get;
+	grid->get_empty_field = grid_get_empty_field;
+	grid->size = size;
+	grid->row_count = 0;
+	grid->rows = (row_t *)calloc(size, sizeof(row_t));
+	grid->fields = (field_t *)calloc(size*size, sizeof(field_t));
+	unsigned int field_index = 0;
+	for(unsigned int irow = 0; irow < size; irow++){
+		row_t * row = new_row(size);
+		row->index = grid->row_count;
+		row->column_count = size;
+		grid->row_count++;
+		grid->rows[row->index] = *row;
+		for(unsigned int icol = 0; icol < size; icol++){
+			field_t * field = new_field();
+			field->column = icol;
+			field->row = irow;
+			field->index = field_index;
+			//field->box = get_box_letter(grid, irow, icol);
+			row->columns[icol] = *field;
+			grid->fields[field_index] = *field;
+			grid->field_count++;
+			field_index++;
+		}
+	}
+	return grid;
+}
+#endif