fix(tests): subpaths_window tests wait for index readiness after #1595 chunked load (#1621)

## Why master is red

After PRs #1592 (route-window subpath regression test) and #1595
(background/chunked index build with 503 readiness gate) were merged
together, two tests in `cmd/server/subpaths_window_test.go` started
failing on master:

```
--- FAIL: TestSubpathsHonorsTimeWindow_StoreLevel
    subpaths_window_test.go:70: unbounded: expected totalPaths=2, got 0 (subpaths=[])
--- FAIL: TestSubpathsHandlerHonorsTimeWindow
    subpaths_window_test.go:116: GET /api/analytics/subpaths?...: status=503 body={"error":"index loading","retryAfter":5}
```

Both branches passed in isolation; the conflict only manifested
post-merge. Reason:

- **#1592** added tests that call `store.Load()` then immediately query
`GetAnalyticsSubpathsWithWindow` / hit `/api/analytics/subpaths`.
- **#1595** moved the subpath + path-hop index builds off the critical
path of `Load()` into background goroutines, and hard-gated the
analytics handlers behind `SubpathIndexReady()` (returning 503 +
`Retry-After: 5` until the build completes).

So after `Load()` returns, `s.spIndex` is still empty for a short window
and the handler returns 503. The store-level test sees `totalPaths=0`;
the handler test sees the 503.

## Fix (test-only)

Add `store.WaitIndexesReady(5 * time.Second)` between `Load()` and the
assertions in both tests. This matches the established pattern already
used by `routes_test.go` and `repeater_enrich_recomputer_1008_test.go`.

The 503 readiness gate from #1595 is intentional production behavior and
is **not** touched. No production code is modified.

## Repro

Before:
```
$ go test ./cmd/server/ -run TestSubpaths.*Window -v -count=1
--- FAIL: TestSubpathsHonorsTimeWindow_StoreLevel (0.01s)
    subpaths_window_test.go:70: unbounded: expected totalPaths=2, got 0 (subpaths=[])
--- FAIL: TestSubpathsHandlerHonorsTimeWindow (0.02s)
    subpaths_window_test.go:116: GET /api/analytics/subpaths?minLen=2&maxLen=8: status=503 body={"error":"index loading","retryAfter":5}
FAIL
```

After:
```
$ go test ./cmd/server/ -run TestSubpaths.*Window -v -count=3
--- PASS: TestSubpathsHonorsTimeWindow_StoreLevel (0.01s)
--- PASS: TestSubpathsHandlerHonorsTimeWindow (0.02s)
... (x3) ...
PASS
ok      github.com/corescope/server     0.097s

$ go test ./cmd/server/ -count=1 -timeout 300s
ok      github.com/corescope/server     46.292s
```

## Files changed
- `cmd/server/subpaths_window_test.go` (+11 lines, test-only)

## Notes
- TDD exemption: this is a test-fix PR for a merge-conflict-induced
failure. The "failing test" already exists on master; this PR makes it
pass correctly by waiting on the readiness gate the test was previously
unaware of.
- Unblocks staging deploys.

Co-authored-by: openclaw-bot <bot@openclaw>

cmd/server/subpaths_window_test.go

@@ -62,6 +62,11 @@ func TestSubpathsHonorsTimeWindow_StoreLevel(t *testing.T) {
 	if err := store.Load(); err != nil {
 		t.Fatalf("store.Load failed: %v", err)
 	}
+	// #1008: indexes build in the background after Load(); tests that
+	// read s.spIndex / s.spTxIndex must wait for the ready flag.
+	if !store.WaitIndexesReady(5 * time.Second) {
+		t.Fatalf("indexes not ready after 5s")
+	}
 
 	// Unbounded: should see both transmissions and their subpaths.
 	all := store.GetAnalyticsSubpathsWithWindow("", 2, 8, 100, TimeWindow{})
@@ -101,6 +106,12 @@ func TestSubpathsHandlerHonorsTimeWindow(t *testing.T) {
 	if err := store.Load(); err != nil {
 		t.Fatalf("store.Load failed: %v", err)
 	}
+	// #1008: handler is hard-gated behind SubpathIndexReady() and returns
+	// 503 until the background build completes. Wait for ready before
+	// hitting the route.
+	if !store.WaitIndexesReady(5 * time.Second) {
+		t.Fatalf("indexes not ready after 5s")
+	}
 	srv.store = store
 
 	mustGet := func(url string) map[string]interface{} {