fix(provider): list models in one page for Anthropic and Gemini

Model discovery used each API's default page size: 20 for Anthropic and
50 for Gemini. A full catalog needed several sequential requests, and at
pod start that overran the 5s warm-fill budget. One replica then
logged "initial discovery ... context deadline exceeded" and went
without that provider's models until the next probe. Every page now
asks for the documented maximum of 1000: Anthropic limit and Gemini
pageSize. Gemini gets pageSize on each page, because it requires the
same parameters across one listing.

Claude-Session: https://claude.ai/code/session_01V5jYJNxpDFdJkyyExpADrv

provider_anthropic.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -270,11 +271,18 @@ type anthropicModelsPayload struct {
 // anthropicListModelsPageCap bounds how many pages listModels follows
 // (M7 fix): a misbehaving upstream that never reports has_more:false, or
 // whose last_id never advances, would otherwise page forever. 20 pages
-// at Anthropic's own default page size (20 per page) covers 400 models —
-// comfortably above any real catalog as of this writing — without
-// risking an unbounded discovery loop against a single provider.
+// at anthropicListModelsPageSize covers far more models than any real
+// catalog without risking an unbounded discovery loop against a single
+// provider.
 const anthropicListModelsPageCap = 20
 
+// anthropicListModelsPageSize is the `limit` sent on every /v1/models
+// page: Anthropic's documented maximum (default 20, range 1-1000). At the
+// default page size a full catalog took several sequential requests, which
+// could overrun registry.go's warmFillTimeout at pod start; one request
+// at the maximum returns the whole catalog.
+const anthropicListModelsPageSize = 1000
+
 // listModels implements providerAdapter: GET {base}/v1/models, following
 // Anthropic's has_more/last_id cursor pagination (M7 fix) via the
 // after_id query parameter, up to anthropicListModelsPageCap pages —
@@ -307,10 +315,12 @@ func (a *anthropicAdapter) listModels(ctx context.Context) ([]string, error) {
 // model ids alongside has_more/last_id for listModels' own pagination
 // loop above.
 func (a *anthropicAdapter) listModelsPage(ctx context.Context, afterID string) (ids []string, hasMore bool, lastID string, err error) {
-	endpoint := a.baseURL + anthropicModelsPath
+	query := url.Values{}
+	query.Set("limit", strconv.Itoa(anthropicListModelsPageSize))
 	if afterID != "" {
-		endpoint += "?after_id=" + url.QueryEscape(afterID)
+		query.Set("after_id", afterID)
 	}
+	endpoint := a.baseURL + anthropicModelsPath + "?" + query.Encode()
 	resp, err := upstreamJSON(ctx, a.client, http.MethodGet, endpoint, a.requestHeaders(false), nil, a.retry, a.timeout, a.adapterName)
 	if err != nil {
 		return nil, false, "", err