feat(web): read admin lanes from the durable pass log, not a poller snapshot (#145)

The Lanes page now projects store.LatestLanePasses and the owner-window
outcomes (store.LanePassOutcomes) into per-Site rows instead of reading an
in-memory Poller snapshot, so a deploy answers the instant the store is up.
Browser configuration is a config fact and reachability is derived from
recent browser-Site passes inside latest.RefuseBackoff.

This atomically deletes the in-memory path in the same commit that makes the
page read the DB: latest/status.go (LaneState, Status, LaneStatus,
recordLaneState) and the web.LaneReporter seam plus fakeLanes are gone, and
latest.refuseBackoff is renamed latest.RefuseBackoff at every callsite.
ownerWindow (#142) is referenced, never declared (contract C2)

docs/adr/0012-persisted-lane-state.md

@@ -0,0 +1,44 @@
+# ADR-0012: Persisted lane state
+
+Date: 2026-08-21
+Status: accepted
+
+Supersedes the in-memory lane snapshot carried by `latest`'s `LaneState`/`Status`
+and the `web.LaneReporter` seam (ADR-0010 wrote the durable rows this page now
+reads).
+
+## Decision
+
+The admin Lanes page stops reading the poller's in-memory Lane state and
+becomes a read of `poll_passes`/`poll_lanes` in Postgres. There is no
+`LaneReporter` interface: `web/admin_lanes.go` walks `store.LatestLanePasses()`
+into one row per Site and adds the window's outcome sums from
+`store.LanePassOutcomes()`. The `latest` package's `LaneState`/`Status` snapshot
+and its `web.LaneReporter` seam are deleted.
+
+The browser is a deployment configuration fact plus a reachability derived
+from the pass log: `BROWSER_WS_URL` set means "configured", and the browser is
+"reachable" unless a recent browser-Site pass inside `latest.RefuseBackoff` is
+a sidecar loss, a missing fetcher, or an interrupted read. A skip reason is
+the whole difference between a Lane resting and a Lane stuck: a skipped pass
+prints its sentence, and only an empty skip with Series due and none read
+draws the true-stall fault. Sleep skips never count toward `Attention`.
+
+## Why
+
+The old page lived on a poller snapshot. Because that state was in memory, a
+deploy erased it: the page read zeroes until a fresh pass ran, and browser
+reachability came through a reporter interface only a live poller could
+serve. Making the page answer from the database means a restart is complete
+the instant the store is up, the browser fact survives a poller restart, and
+a Lane that has not yet gathered figures shows a placeholder rather than a
+confident zero.
+
+## Constraints
+
+The poller still owns the writes: each pass exit records one row (ADR-0010),
+and a pass that returns before gathering figures carries the previous pass's
+numbers forward instead of recording zeroes. A skip is a stable wire string;
+`asleep` never counts toward `Attention`. When polling is switched off the
+page must say so, and the browser statusline appears only when a poller
+actually answers.