docs(latest): correct the browser-site comments the comix change made stale

Review findings from #98: BrowserFetcher's doc still described two sites and
two read shapes, Get's doc enumerated them a second time, and the Fallback
field doc omitted comix. The comix fixture comment now records the live
in-tab body it was re-checked against.

backend/internal/latest/browser.go

@@ -44,10 +44,11 @@ var comixSeriesPathRe = regexp.MustCompile(`^/title/[^/?#]+/?$`)
 // sync that break silently and separately. The browser's own cookie jar
 // persists across polls, so the challenge is solved once every few hours.
 //
-// The two sites differ in how the chapter list is read: kagane serves it from
-// a JSON API that must be called from inside the page (so the request carries
-// the clearance cookie), while novelfull renders it into the HTML so the
-// cleared DOM is the payload.
+// The three sites differ in what a cleared tab is asked for: kagane fetches a
+// JSON API from inside the page (the list exists nowhere else), comix fetches
+// its own Series URL from inside the page (the served HTML carries the facts,
+// and rendering the SPA costs ~65 requests instead of one), and novelfull
+// renders its list into the HTML so the cleared DOM is the payload.
 type BrowserFetcher struct {
 	allocCtx context.Context
 	cancel   context.CancelFunc
@@ -91,10 +92,9 @@ func (f *BrowserFetcher) Close() {
 }
 
 // Get navigates to seriesURL, lets any challenge resolve, then reads the
-// payload the Site's registry entry describes — kagane's chapter-list API from
-// inside the page so the request carries the clearance cookie, novelfull's
-// served HTML. The returned body is whatever the Site's chapter list lives in,
-// which is what the entry's LatestChapter parse expects.
+// payload the Site's registry entry describes (the shapes are listed on
+// BrowserFetcher). The returned body is whatever the Site's chapter list lives
+// in, which is what the entry's LatestChapter parse expects.
 func (f *BrowserFetcher) Get(ctx context.Context, seriesURL string) (string, int, error) {
 	var body string
 	// Sorted order (browserBackedSites sorts) makes dispatch deterministic: