feat: implement keyboard and mouse input, pattern placement, and HiDPI scaling

Add configurable key bindings (TOML), modifier-aware dispatch, mouse-driven
pattern placement with preview and rotation, cell grid storage/rendering,
and fractional/integer HiDPI scaling. Archive the input-and-placement change
and sync its specs to main specs.

Tests: Hashtable, Config, Grid, Pattern (4/4 pass).

tests/test_config.c

@@ -0,0 +1,49 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <xkbcommon/xkbcommon.h>
+
+#include "config.h"
+
+int main(void) {
+    uint32_t mods;
+    char *key = NULL;
+
+    assert(config_parse_mods("ctrl+q", &mods, &key) == 0);
+    assert(mods == MOD_CTRL);
+    assert(strcmp(key, "q") == 0);
+    free(key);
+
+    assert(config_parse_mods("space", &mods, &key) == 0);
+    assert(mods == 0);
+    assert(strcmp(key, "space") == 0);
+    free(key);
+
+    assert(config_parse_action("quit") == ACTION_QUIT);
+    assert(config_parse_action("select:glider") == ACTION_SELECT_GLIDER);
+    assert(config_parse_action("nope") == ACTION_NONE);
+
+    config_t cfg = config_defaults();
+    xkb_keysym_t one = xkb_keysym_from_name("1", XKB_KEYSYM_CASE_INSENSITIVE);
+    xkb_keysym_t space = xkb_keysym_from_name("space", XKB_KEYSYM_CASE_INSENSITIVE);
+    assert(config_lookup(&cfg, 0, one) == ACTION_SELECT_GLIDER);
+    assert(config_lookup(&cfg, 0, space) == ACTION_ROTATE);
+
+    const char *path = "/tmp/opencode/test_keys.conf";
+    FILE *fp = fopen(path, "w");
+    assert(fp);
+    fputs("[bindings]\n\"1\" = \"quit\"\n", fp);
+    fclose(fp);
+
+    config_t cfg2 = config_load(path);
+    assert(config_lookup(&cfg2, 0, one) == ACTION_QUIT);
+    assert(config_lookup(&cfg2, 0, space) == ACTION_ROTATE);
+
+    config_free(&cfg);
+    config_free(&cfg2);
+    remove(path);
+    printf("config tests passed\n");
+    return 0;
+}

tests/test_grid.c

@@ -0,0 +1,25 @@
+#include <assert.h>
+#include <stdio.h>
+
+#include "grid.h"
+
+int main(void) {
+    grid_t g;
+    grid_init(&g, 4, 4);
+    assert(grid_get(&g, 0, 0) == 0);
+    grid_set(&g, 1, 2, 1);
+    assert(grid_get(&g, 1, 2) == 1);
+    assert(grid_get(&g, -1, 0) == 0);
+    assert(grid_get(&g, 4, 4) == 0);
+
+    grid_set(&g, 0, 0, 1);
+    grid_resize(&g, 6, 2);
+    assert(grid_get(&g, 0, 0) == 1);
+    assert(grid_get(&g, 1, 2) == 0);
+    grid_clear(&g);
+    assert(grid_get(&g, 0, 0) == 0);
+
+    grid_free(&g);
+    printf("grid tests passed\n");
+    return 0;
+}

tests/test_pattern.c

@@ -0,0 +1,28 @@
+#include <assert.h>
+#include <stdio.h>
+
+#include "pattern.h"
+
+int main(void) {
+    assert(pattern_count() == 4);
+    const void *p = pattern_get(0);
+    (void)p;
+    int dx[16], dy[16];
+    int n = pattern_rotated_offsets(0, 0, dx, dy);
+    assert(n == 5);
+
+    int w, h;
+    pattern_bounds(0, 1, &w, &h);
+    assert(w == 3 && h == 3);
+
+    int dx2[16], dy2[16];
+    pattern_rotated_offsets(0, 1, dx2, dy2);
+    int same = 1;
+    for (int i = 0; i < n; i++) {
+        if (dx[i] != dx2[i] || dy[i] != dy2[i]) same = 0;
+    }
+    assert(!same);
+
+    printf("pattern tests passed\n");
+    return 0;
+}