feat(library): manga spec — jikan enrich, rss/mangadex chapter flip

tests/fixtures/canonical-manga.md

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+---
+type: manga_item
+title: Chainsaw Man
+eng_name: 
+read_status: Reading
+rating: 4
+rating_stars: ⭐️⭐️⭐️⭐️
+last_read_chapter: 210
+latest_chapter: 213
+last_chapter_date: 2026-07-16
+chapters: null
+volumes: null
+status: Publishing
+authors: ["Fujimoto, Tatsuki"]
+genre: [Action, Horror, Sports]
+score: 8.7
+published_from: 2018-12-03
+published_to: null
+mal_id: 116778
+mangadex_id: abc-123
+rss: "https://example.com/csm-feed.xml"
+poster: "https://cdn.myanimelist.net/images/manga/3/216464l.jpg"
+url: "https://myanimelist.net/manga/116778/Chainsaw_Man"
+tags: [mangas, manga]
+---
+
+# Chainsaw Man
+
+![poster|200](https://cdn.myanimelist.net/images/manga/3/216464l.jpg)
+
+**Manga** · Publishing · 8.7
+
+**Read Status:** Reading
+**Progress:** ch. 210 / 213
+
+## Synopsis
+Denji has been robbed of a normal life ever since his Chainsaw Devil, Pochita, merged with him.
+
+**Authors:** Fujimoto, Tatsuki
+
+## Links
+- [MAL page](https://myanimelist.net/manga/116778/Chainsaw_Man)
+- [RSS feed](https://example.com/csm-feed.xml)
+
+## My Notes
+

tests/fixtures/jikan-manga-csm.json

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+{
+	"data": {
+		"mal_id": 116778,
+		"url": "https://myanimelist.net/manga/116778/Chainsaw_Man",
+		"images": {
+			"jpg": {
+				"image_url": "https://cdn.myanimelist.net/images/manga/3/216464.jpg",
+				"large_image_url": "https://cdn.myanimelist.net/images/manga/3/216464l.jpg"
+			}
+		},
+		"title": "Chainsaw Man",
+		"title_english": "Chainsaw Man",
+		"title_japanese": "チェンソーマン",
+		"titles": [
+			{ "type": "Default", "title": "Chainsaw Man" },
+			{ "type": "Japanese", "title": "チェンソーマン" },
+			{ "type": "English", "title": "Chainsaw Man" }
+		],
+		"type": "Manga",
+		"chapters": null,
+		"volumes": null,
+		"status": "Publishing",
+		"publishing": true,
+		"published": {
+			"from": "2018-12-03T00:00:00+00:00",
+			"to": null
+		},
+		"score": 8.73,
+		"scored_by": 42000,
+		"rank": 12,
+		"popularity": 3,
+		"synopsis": "Denji has been robbed of a normal life ever since his Chainsaw Devil, Pochita, merged with him. Now, he'll hunt down devils with his devil-dog powers and try to survive in a world that sees him as a weapon.",
+		"authors": [{ "mal_id": 1, "type": "people", "name": "Fujimoto, Tatsuki" }],
+		"genres": [
+			{ "mal_id": 1, "type": "manga", "name": "Action" },
+			{ "mal_id": 8, "type": "manga", "name": "Horror" },
+			{ "mal_id": 30, "type": "manga", "name": "Sports" }
+		]
+	}
+}

tests/fixtures/mangadex-feed.json

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+{
+	"result": "ok",
+	"response": "collection",
+	"data": [
+		{
+			"id": "b1a2c3d4-0000-1111-2222-333344445555",
+			"type": "chapter",
+			"attributes": {
+				"chapter": "214",
+				"title": "",
+				"translatedLanguage": "en",
+				"publishAt": "2026-07-30T11:00:00+00:00",
+				"readableAt": "2026-07-30T12:00:00+00:00"
+			}
+		}
+	],
+	"limit": 1,
+	"offset": 0,
+	"total": 214
+}