feat(latest): parse comix SSR state and kagane API for latest chapter

backend/internal/latest/sites_test.go

@@ -34,6 +34,24 @@ const challengeFixture = `<!DOCTYPE html><html><head><title>Just a moment...</ti
 <script src="/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1"></script></head>
 <body><div id="challenge-running">Checking your browser</div></body></html>`
 
+// Trimmed from the server-rendered HTML of
+// https://comix.to/title/n8we-dungeons-and-crayons fetched 2026-08-03. comix is
+// an SPA: the page ships a JSON state blob rather than a list of chapter
+// anchors, and latestChapterUrl is where the newest chapter actually lives.
+const comixSeriesFixture = `
+{"firstChapterUrl":"/title/n8we-dungeons-and-crayons/5038739-chapter-1","latestChapterUrl":"/title/n8we-dungeons-and-crayons/11139891-chapter-80"},
+{""manga","recommended","n8we",1]":{"items":[{"latestChapterUrl":"/title/qqwrm-full-time-awakening/99999999-chapter-999"}]}
+`
+
+// The kagane branch is fed by the browser fetcher, so the body is API JSON, not
+// HTML. Trimmed from GET /api/v2/series/<uuid> on 2026-08-03.
+const kaganeAPIFixture = `
+{"series_id":"019f84bc-9ba0-7ed9-86f5-8b905ec7c28b","title":"Infinite Decryption",
+"series_books":[{"book_id":"a","title":"Episode 1","chapter_no":"1","sort_no":1},
+{"book_id":"b","title":"Episode 41","chapter_no":"41","sort_no":41},
+{"book_id":"c","title":"Episode 40.5","chapter_no":"40.5","sort_no":40}]}
+`
+
 func TestLatestChapterFrom(t *testing.T) {
 	const asuraURL = "https://asurascans.com/comics/chronicles-of-the-demon-faction-f886a8af"
 	const demonicURL = "https://demonicscans.org/manga/Catastrophic-Necromancer"
@@ -100,6 +118,34 @@ func TestLatestChapterFrom(t *testing.T) {
 			site: "mangadex", seriesURL: "https://example.com/x", body: asuraSeriesFixture,
 			wantOK: false,
 		},
+		{
+			name:      "comix reads latestChapterUrl, scoped to this series",
+			site:      "comix",
+			seriesURL: "https://comix.to/title/n8we-dungeons-and-crayons",
+			body:      comixSeriesFixture,
+			wantOK:    true, wantNum: 80, wantLabel: "Chapter 80",
+		},
+		{
+			name:      "comix yields nothing on a challenge page",
+			site:      "comix",
+			seriesURL: "https://comix.to/title/n8we-dungeons-and-crayons",
+			body:      challengeFixture,
+			wantOK:    false,
+		},
+		{
+			name:      "kagane takes the max chapter_no from API json",
+			site:      "kagane",
+			seriesURL: "https://kagane.to/series/019f84bc-9ba0-7ed9-86f5-8b905ec7c28b",
+			body:      kaganeAPIFixture,
+			wantOK:    true, wantNum: 41, wantLabel: "Chapter 41",
+		},
+		{
+			name:      "kagane yields nothing on a challenge page",
+			site:      "kagane",
+			seriesURL: "https://kagane.to/series/019f84bc-9ba0-7ed9-86f5-8b905ec7c28b",
+			body:      challengeFixture,
+			wantOK:    false,
+		},
 	}
 
 	for _, tt := range tests {