fix(adapters): ground native schemas, merge-not-replace, add goose/cagent/zed

- common/mcp.go: MCPStyle enum + BuildMCPMapStyled for claude/crush/opencode/zed dialects
- common/jsonmerge.go: MergeJSONKeys (JSON-first, JSONC fallback) preserves user keys;
  fix: try plain json.Unmarshal before StripJSONComments to avoid mangling URLs with //
- common/yamlmerge.go: MergeYAMLKeys for YAML configs (goose)
- common/blocks.go: add ProvidersAsMap for opencode map-shaped provider key
- claudecode: merge settings.json (preserves hooks/permissions/env); MCPClaudeStyle (no type field)
- crush: fix mcp key (was mcpServers); MCPCrushStyle entries include type field; merge crush.json; fix import key mcp
- kilo: drop providers key (kilo has none); MCPOpencodeStyle (local/remote); merge kilo.json
- opencode: fix provider (singular map) + model (not default_model); MCPOpencodeStyle; merge jsonc; fix import key mcp
- goose: new adapter — YAML merge, extensions map, splitProviderModel, import reconstructs MCP from extensions
- cagent: new adapter — renders starter default.yaml, import returns empty
- zed: new adapter — merge settings.json, context_servers (MCPZedStyle) + agent.default_model
- docs: append Grounded harness schemas section to design spec

internal/adapter/common/blocks.go

@@ -48,6 +48,45 @@ func buildModels(models []canonical.Model) []map[string]any {
 	return out
 }
 
+// ProvidersAsMap returns a name-keyed map of provider objects for harnesses
+// like opencode that use `provider` (singular, map-shaped) instead of a slice.
+// The gateway entry is keyed "harness-sync-gateway"; upstreams use their name.
+func ProvidersAsMap(p *canonical.Profile) map[string]any {
+	out := map[string]any{}
+	if p.Gateway.URL != "" {
+		entry := map[string]any{
+			"name": "harness-sync gateway",
+			"options": map[string]any{
+				"baseURL": p.Gateway.URL,
+				"apiKey":  p.Gateway.Token,
+			},
+		}
+		if models := buildModels(p.Models); len(models) > 0 {
+			modelsMap := map[string]any{}
+			for _, m := range p.Models {
+				modelsMap[m.ID] = map[string]any{"name": m.ID}
+			}
+			entry["models"] = modelsMap
+		}
+		out["harness-sync-gateway"] = entry
+	}
+	for _, up := range p.Upstreams {
+		entry := map[string]any{"name": up.Name}
+		opts := map[string]any{}
+		if up.BaseURL != "" {
+			opts["baseURL"] = up.BaseURL
+		}
+		if up.APIKey != "" {
+			opts["apiKey"] = up.APIKey
+		}
+		if len(opts) > 0 {
+			entry["options"] = opts
+		}
+		out[up.Name] = entry
+	}
+	return out
+}
+
 // BuildMCPMap returns canonical MCP servers as a name -> object map.
 // Empty map (not nil) is returned when there are no servers so the caller
 // can decide whether to include the key.