Stable Asura series IDs: strip rotating build hash (#6)

Asura series slugs carry a site-wide build hash (-059befe1) that rotates on every redeploy, silently orphaning all asura bookmarks (old-hash URLs 302 to new-hash ones, so detect() yields keys that never match stored rows).

Backend:
- migrateAsuraKeys in OpenStore: one-off idempotent migration rewriting hashed asura keys to the stable hashless ID, merging collisions to newest updated_at; losers deleted before winner rewrite (PK-collision safe) — regression tests included
- poller latestChapterFrom: build hash made optional in chapter-scoping regex so latest_chapter survives redeploys

Userscript:
- stripBuildHash(/-[0-9a-f]{8}$/) applied to seriesId in both asura detect branches; URLs keep full slug (stale hashes 302)
- load-time migration rewrites cached + retry-queued asura keys to the stripped form so a queued PUT cannot resurrect an orphaned row

Docs: AGENTS.md + CLAUDE.md URL-shape notes; design spec at docs/superpowers/specs/2026-07-28-asura-stable-series-id-design.md

Verified: go test -count=1 ./... green (new rotation + collision tests), node --check green, regex verified against live asurascans.com slugs.

Deploy order: backend first (migration runs at OpenStore). Orphan rows created by not-yet-updated userscripts self-heal on next backend restart.

Reviewed-on: #6
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>

backend/latest_sites.go

@@ -14,7 +14,9 @@ type latestChapter struct {
 
 // asuraSlugRe pulls the series slug out of a stored series_url.
 // Shape verified live 2026-07-26: https://asurascans.com/comics/<slug>, where
-// the slug carries a trailing hash-like suffix (e.g. "-f886a8af").
+// the slug carries a trailing build-hash suffix (e.g. "-f886a8af") that
+// rotates on every site redeploy — callers must strip it (asuraBuildHash)
+// before using the slug to scope anything.
 var asuraSlugRe = regexp.MustCompile(`/comics/([^/?#]+)`)
 
 // demonicChapterRe matches the pre-redirect anchors demonic series pages link
@@ -47,9 +49,14 @@ func latestChapterFrom(site, seriesURL, body string) (latestChapter, bool) {
 		if m == nil {
 			return latestChapter{}, false
 		}
+		// Stored URLs predating a redeploy may carry a stale build hash;
+		// chapter hrefs in the fetched body carry the current one. Strip to
+		// the stable ID (same rule as migrateAsuraKeys) and make the hash
+		// optional in the pattern, so scoping survives rotations.
+		slug := asuraBuildHash.ReplaceAllString(m[1], "")
 		// Compiled per call rather than cached: this runs once per fetch, which
 		// is at most a few times a minute, and the slug varies per series.
-		re = regexp.MustCompile(`/comics/` + regexp.QuoteMeta(m[1]) + `/chapter/([0-9.]+)`)
+		re = regexp.MustCompile(`/comics/` + regexp.QuoteMeta(slug) + `(?:-[0-9a-f]{8})?/chapter/([0-9.]+)`)
 	case "demonic":
 		re = demonicChapterRe
 	default: