feat: URL-derived provider keys (hs-<hostname>) + dedup providers sharing same gateway URL

- GatewayProviderKey() derives stable key from gateway URL hostname
  e.g. https://llmgw.h.raczylo.com/v1 → hs-llmgw-h-raczylo-com
- AbsorbDuplicateProviders() merges providers sharing the same baseURL
  into our canonical entry; user-crafted model metadata wins for overlaps
- kilo: renders to opencode.jsonc (primary config), deep-merges providers,
  deletes enabled_providers filter that was hiding our gateway
- opencode: absorbs duplicate providers from existing config
- All adapters use GatewayProviderKey() instead of hardcoded string
- Fix goose URL doubling (was /v1/v1/chat/completions → /chat/completions)
- Fix token propagation: api_key written directly (not env var ref)
- Zed: adds prompt_cache_key capability, deletes context_servers key
  to avoid ContextServerSettingsContent serde untagged-enum parse error

internal/adapters/zed/zed.go

@@ -136,7 +136,7 @@ func zedLanguageModels(p *canonical.Profile) map[string]any {
 	}
 	return map[string]any{
 		"openai_compatible": map[string]any{
-			common.GatewayProviderID: entry,
+			common.GatewayProviderKey(p.Gateway.URL): entry,
 		},
 	}
 }
@@ -156,7 +156,7 @@ func zedAgentBlock(existing []byte, p *canonical.Profile) map[string]any {
 	}
 	if p.Gateway.DefaultModel != "" {
 		base["default_model"] = map[string]any{
-			"provider": common.GatewayProviderID,
+			"provider": common.GatewayProviderKey(p.Gateway.URL),
 			"model":    p.Gateway.DefaultModel,
 		}
 	}

internal/adapters/zed/zed_test.go

@@ -46,16 +46,16 @@ func TestZedRenderProducesExpectedTargets(t *testing.T) {
 	var parsed map[string]any
 	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
 
-	// agent.default_model routes through harness-sync-gateway (openai_compatible provider).
+	// agent.default_model routes through hs-llmgw-example-com (openai_compatible provider).
 	agent := parsed["agent"].(map[string]any)
 	dm := agent["default_model"].(map[string]any)
-	assert.Equal(t, "harness-sync-gateway", dm["provider"])
+	assert.Equal(t, "hs-llmgw-example-com", dm["provider"])
 	assert.Equal(t, "claude-sonnet-4-6", dm["model"])
 
 	// language_models.openai_compatible has our named gateway entry.
 	lm := parsed["language_models"].(map[string]any)
 	oc := lm["openai_compatible"].(map[string]any)
-	gw := oc["harness-sync-gateway"].(map[string]any)
+	gw := oc["hs-llmgw-example-com"].(map[string]any)
 	assert.Equal(t, "https://llmgw.example.com/v1", gw["api_url"])
 
 	// context_servers must be absent — Zed serde untagged-enum bug aborts
@@ -140,8 +140,8 @@ func TestZedRenderEmitsLanguageModelsOpenAICompatible(t *testing.T) {
 	require.True(t, ok, "language_models must be present")
 	oc, ok := lm["openai_compatible"].(map[string]any)
 	require.True(t, ok, "language_models.openai_compatible must be present")
-	gw, ok := oc["harness-sync-gateway"].(map[string]any)
-	require.True(t, ok, "openai_compatible.harness-sync-gateway must be present")
+	gw, ok := oc["hs-gw"].(map[string]any)
+	require.True(t, ok, "openai_compatible.hs-gw must be present")
 	assert.Equal(t, "https://gw", gw["api_url"])
 	avail, ok := gw["available_models"].([]any)
 	require.True(t, ok)