feat(histoires): podcast manifest v2 parser

Pure C parser (cJSON) for /sdcard/podcasts/manifest.json v2
format (shows grouped with cover + episodes list). Skips shows
with zero episodes. SD loader guarded by #ifndef LISAEL_HOST_TEST.
Host test compiles and passes on Mac without IDF toolchain.

main/audio/podcast_manifest.c

@@ -0,0 +1,91 @@
+// See podcast_manifest.h. The pure parser is host-testable (no ESP-IDF deps);
+// the SD loader is compiled only on-target (#ifndef LISAEL_HOST_TEST).
+#include "audio/podcast_manifest.h"
+#include "cJSON.h"
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int lisael_podcast_parse(const char *json, lisael_show_t *shows, int max_shows)
+{
+    if (!json || !shows || max_shows <= 0) {
+        return -1;
+    }
+    cJSON *root = cJSON_Parse(json);
+    if (!cJSON_IsArray(root)) {
+        cJSON_Delete(root);
+        return -1;
+    }
+
+    int n_shows = 0;
+    cJSON *jshow;
+    cJSON_ArrayForEach(jshow, root) {
+        if (n_shows >= max_shows) {
+            break;
+        }
+        cJSON *jname  = cJSON_GetObjectItem(jshow, "show");
+        cJSON *jcover = cJSON_GetObjectItem(jshow, "cover");
+        cJSON *jeps   = cJSON_GetObjectItem(jshow, "episodes");
+        if (!cJSON_IsString(jname) || !cJSON_IsArray(jeps)) {
+            continue;
+        }
+        lisael_show_t *s = &shows[n_shows];
+        memset(s, 0, sizeof(*s));
+        snprintf(s->show, sizeof(s->show), "%s", jname->valuestring);
+        if (cJSON_IsString(jcover)) {
+            snprintf(s->cover, sizeof(s->cover), "%s", jcover->valuestring);
+        }
+        cJSON *jep;
+        cJSON_ArrayForEach(jep, jeps) {
+            if (s->n_eps >= LISAEL_MAX_EPISODES) {
+                break;
+            }
+            cJSON *jf = cJSON_GetObjectItem(jep, "file");
+            cJSON *jt = cJSON_GetObjectItem(jep, "title");
+            if (!cJSON_IsString(jf)) {
+                continue;
+            }
+            lisael_episode_t *e = &s->eps[s->n_eps];
+            snprintf(e->file, sizeof(e->file), "%s", jf->valuestring);
+            snprintf(e->title, sizeof(e->title), "%s",
+                     cJSON_IsString(jt) ? jt->valuestring : jf->valuestring);
+            s->n_eps++;
+        }
+        if (s->n_eps > 0) {
+            n_shows++;  // skip shows with no playable episode
+        }
+    }
+    cJSON_Delete(root);
+    return n_shows;
+}
+
+#ifndef LISAEL_HOST_TEST
+#include "esp_log.h"
+int lisael_podcast_load(lisael_show_t *shows, int max_shows)
+{
+    const char *path = "/sdcard/podcasts/manifest.json";
+    FILE *f = fopen(path, "r");
+    if (!f) {
+        return -1;
+    }
+    fseek(f, 0, SEEK_END);
+    long sz = ftell(f);
+    fseek(f, 0, SEEK_SET);
+    if (sz <= 0 || sz > 64 * 1024) {
+        fclose(f);
+        return -1;
+    }
+    char *buf = malloc((size_t)sz + 1);
+    if (!buf) {
+        fclose(f);
+        return -1;
+    }
+    size_t rd = fread(buf, 1, (size_t)sz, f);
+    buf[rd] = '\0';
+    fclose(f);
+    int n = lisael_podcast_parse(buf, shows, max_shows);
+    free(buf);
+    ESP_LOGI("podcast", "loaded %d show(s) from %s", n, path);
+    return n;
+}
+#endif

main/audio/podcast_manifest.h

@@ -0,0 +1,36 @@
+// Podcast manifest v2 (grouped by show) for the Lisael Box "Histoires" screen.
+// /sdcard/podcasts/manifest.json = JSON array of shows, each with a cover and
+// a list of episodes. ASCII file names; UTF-8 show/title strings.
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Caps kept small: lisael_show_t is ~1.8 KB and the Histoires screen keeps a
+// static array of these. Use static/heap storage, never a task stack.
+#define LISAEL_MAX_SHOWS    8
+#define LISAEL_MAX_EPISODES 12
+
+typedef struct {
+    char file[64];   // audio basename under /sdcard/podcasts/ (e.g. "oli_01.m4a")
+    char title[80];  // UTF-8 display title
+} lisael_episode_t;
+
+typedef struct {
+    char show[48];                              // UTF-8 show name
+    char cover[40];                             // cover basename ("oli.bin"), "" if none
+    lisael_episode_t eps[LISAEL_MAX_EPISODES];
+    int  n_eps;
+} lisael_show_t;
+
+// Pure parser: JSON string -> shows[]. Skips shows with zero episodes.
+// Returns show count (>=0), or -1 if the JSON is not a valid array.
+int lisael_podcast_parse(const char *json, lisael_show_t *shows, int max_shows);
+
+// Read /sdcard/podcasts/manifest.json and parse it. Returns count or -1.
+int lisael_podcast_load(lisael_show_t *shows, int max_shows);
+
+#ifdef __cplusplus
+}
+#endif

test/host/test_podcast_manifest.c

@@ -0,0 +1,41 @@
+// Host unit test for the v2 podcast manifest parser.
+#define LISAEL_HOST_TEST
+#include "audio/podcast_manifest.h"
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+static const char *SAMPLE =
+"[{\"show\":\"Une histoire et Oli\",\"cover\":\"oli.bin\",\"episodes\":["
+  "{\"file\":\"oli_01.m4a\",\"title\":\"Concert p.1\"},"
+  "{\"file\":\"oli_02.m4a\",\"title\":\"Concert p.2\"}]},"
+ "{\"show\":\"Bestioles\",\"cover\":\"bestioles.bin\",\"episodes\":["
+  "{\"file\":\"bestioles_01.mp3\",\"title\":\"La gerboise\"}]},"
+ "{\"show\":\"Vide\",\"episodes\":[]}]";
+
+int main(void) {
+    lisael_show_t shows[LISAEL_MAX_SHOWS];
+    int n = lisael_podcast_parse(SAMPLE, shows, LISAEL_MAX_SHOWS);
+    assert(n == 2);                                       // empty show skipped
+    assert(strcmp(shows[0].show, "Une histoire et Oli") == 0);
+    assert(strcmp(shows[0].cover, "oli.bin") == 0);
+    assert(shows[0].n_eps == 2);
+    assert(strcmp(shows[0].eps[1].file, "oli_02.m4a") == 0);
+    assert(strcmp(shows[0].eps[0].title, "Concert p.1") == 0);
+    assert(strcmp(shows[1].show, "Bestioles") == 0);
+    assert(shows[1].n_eps == 1);
+    assert(lisael_podcast_parse("not json", shows, LISAEL_MAX_SHOWS) == -1);
+
+    // title falls back to the file name when "title" is absent
+    lisael_show_t s2[LISAEL_MAX_SHOWS];
+    int m = lisael_podcast_parse(
+        "[{\"show\":\"S\",\"episodes\":[{\"file\":\"a.mp3\"}]}]", s2, LISAEL_MAX_SHOWS);
+    assert(m == 1 && s2[0].n_eps == 1);
+    assert(strcmp(s2[0].eps[0].title, "a.mp3") == 0);
+
+    // guard clauses
+    assert(lisael_podcast_parse(NULL, s2, LISAEL_MAX_SHOWS) == -1);
+    assert(lisael_podcast_parse("[]", s2, 0) == -1);
+    printf("OK: %d shows\n", n);
+    return 0;
+}