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/jsonmerge_test.go

@@ -0,0 +1,80 @@
+package common
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMergeJSONKeysPreservesOtherKeys(t *testing.T) {
+	existing := []byte(`{"a":1,"b":2}`)
+	overlay := map[string]any{"b": 3, "c": 4}
+	out, err := MergeJSONKeys(existing, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, float64(1), m["a"])
+	assert.Equal(t, float64(3), m["b"])
+	assert.Equal(t, float64(4), m["c"])
+}
+
+func TestMergeJSONKeysEmptyExisting(t *testing.T) {
+	overlay := map[string]any{"x": "y"}
+	out, err := MergeJSONKeys(nil, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, "y", m["x"])
+	assert.Len(t, m, 1)
+}
+
+func TestMergeJSONKeysInvalidExisting(t *testing.T) {
+	existing := []byte(`not json at all`)
+	overlay := map[string]any{"k": "v"}
+	out, err := MergeJSONKeys(existing, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, "v", m["k"])
+	assert.Len(t, m, 1)
+}
+
+func TestMergeJSONKeysNilOverlayValueDeletesKey(t *testing.T) {
+	existing := []byte(`{"a":1,"b":2}`)
+	overlay := map[string]any{"b": nil}
+	out, err := MergeJSONKeys(existing, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, float64(1), m["a"])
+	assert.NotContains(t, m, "b")
+}
+
+func TestMergeJSONKeysJSONC(t *testing.T) {
+	existing := []byte(`// comment
+{
+  "a": 1, // trailing
+  /* block */ "b": 2
+}`)
+	overlay := map[string]any{"c": 3}
+	out, err := MergeJSONKeys(existing, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, float64(1), m["a"])
+	assert.Equal(t, float64(2), m["b"])
+	assert.Equal(t, float64(3), m["c"])
+}
+
+func TestMergeJSONKeysTrailingNewline(t *testing.T) {
+	out, err := MergeJSONKeys(nil, map[string]any{"k": "v"})
+	require.NoError(t, err)
+	assert.Equal(t, '\n', rune(out[len(out)-1]))
+}