Spec #136: Finished belongs to the Series — owner-owned poll gate, Lifecycle bucket dropped (#163)

Closes #136.

Spec #136 end to end: `finished` becomes a fact about the Series, written only by the owner, and the reader-facing Lifecycle bucket is gone.

## What landed

- **#157** — `series.finished_at bigint NOT NULL DEFAULT 0` plus the migration whose statement order is load-bearing (seed from the buckets, then flip them); both Lane queries lose the `HAVING COUNT(*) FILTER (WHERE b.status <> 'finished')` clause and gate on `finished_at = 0` instead, with the due-query/eligible-count force asymmetry kept deliberate and commented; `StatusFinished`, its API special-case 400, the web tab and the templates' Finished bucket deleted.
- **#158** — owner Finish control on the Series detail page: confirm-gated finish, instant un-finish, admin accent (never ember, nothing is destroyed), `Store.SetSeriesFinished`, the two routes behind the owner gate, and the state displayed on the list row without offering the control there.
- **#160** — reader side: derived `finished` bool on the flat Bookmark (`s.finished_at > 0`), rendered as a text-only label in both userscripts and on the web card; read-only inbound by omission from `Upsert`'s explicit `series` column list, same mechanism that already protects `cover`.
- **#161** — glossary and the stale Reader-count divergence note catch up.
- **#159** — `finished` joins the admin filter vocabulary (predicate `finished_at > 0`, label `Finished`, own aggregate count, figure last in the stats block as informational); the four clock-driven hygiene predicates (stale, never-checked, no-cover, no-chapter) exclude finished Series while unpollable, orphan and sighting-raised deliberately do not.

## Verification

`go vet ./...` and `go test ./...` green on the merged branch (Docker-backed, throwaway `postgres:17-alpine` per package). Each ticket also passed a two-axis review (spec + standards) on its own branch before merge.

Reviewed-on: #163
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>

userscript/test/logic.test.js

@@ -58,6 +58,7 @@ const {
   anchorsFromHTML,
   statusOf,
   kindOf,
+  finishedLabel,
 } = require("../manga-bookmark.user.js");
 
 // detect() reads only these four properties off location.
@@ -395,7 +396,18 @@ test("statusOf defaults a missing status to reading", () => {
   assert.equal(statusOf({}), "reading");
   assert.equal(statusOf({ status: "" }), "reading");
   assert.equal(statusOf({ status: "archived" }), "archived");
-  assert.equal(statusOf({ status: "finished" }), "finished");
+});
+
+// ============================================================
+// finishedLabel — finished is a fact about the Series (issue #157), which is
+// the server's business; the panel only names it. The label is text through
+// the el() helper, never markup.
+// ============================================================
+
+test("finishedLabel names a finished series and nothing else", () => {
+  assert.equal(finishedLabel({ finished: true }), "Finished");
+  assert.equal(finishedLabel({ finished: false }), "");
+  assert.equal(finishedLabel({}), "");
 });
 
 // ============================================================