fix(zed): switch to language_models.openai_compatible for Agent panel visibility

The Zed Agent panel (new ACP-based UI) only discovers providers registered
under language_models.openai_compatible.<name>, not language_models.openai.
Each named entry appears as its own provider in the LLM Providers list.

- language_models.openai_compatible.harness-sync-gateway holds gateway URL + models
- agent.default_model.provider = 'harness-sync-gateway' (was 'openai')
- Model entries include capabilities {tools,images,parallel_tool_calls}
- Export common.GatewayProviderID so zed.go can reference it
- Fix staticcheck QF1001 (De Morgan's law) in io.go
- Fix struct field alignment in File (80→72 bytes)
- gofmt remaining files

internal/adapter/adapter.go

@@ -23,9 +23,22 @@ func (k Kind) String() string {
 	return "unknown"
 }
 
+// HarnessCapabilities declares what an adapter manages.
+// HasBuiltInSub means the harness has its own AI subscription (e.g. Claude Max)
+// and harness-sync should not write provider/model/endpoint config for it.
+type HarnessCapabilities struct {
+	ManagesProviders    bool // writes provider/gateway endpoint config
+	ManagesModels       bool // writes model selection config
+	ManagesMCP          bool // writes MCP server config
+	ManagesSkills       bool // writes skills symlink or equivalent
+	ManagesInstructions bool // writes instructions file (CLAUDE.md, AGENTS.md, etc.)
+	HasBuiltInSub       bool // has its own subscription; provider/model config is skipped
+}
+
 type Adapter interface {
 	Name() string
 	Detect() bool
+	Capabilities() HarnessCapabilities
 	Render(b *canonical.Bundle) (*FileSet, error)
 	Import(home string) (*ImportResult, error)
 }

internal/adapter/adapter_test.go

@@ -34,6 +34,7 @@ func (f *fakeAdapter) Name() string                                 { return f.n
 func (f *fakeAdapter) Detect() bool                                 { return f.detect }
 func (f *fakeAdapter) Render(_ *canonical.Bundle) (*FileSet, error) { return NewFileSet(), nil }
 func (f *fakeAdapter) Import(_ string) (*ImportResult, error)       { return &ImportResult{}, nil }
+func (f *fakeAdapter) Capabilities() HarnessCapabilities            { return HarnessCapabilities{} }
 
 func TestRegistry(t *testing.T) {
 	r := NewRegistry()

internal/adapter/common/blocks.go

@@ -10,6 +10,9 @@ import (
 
 const gatewayProviderID = "harness-sync-gateway"
 
+// GatewayProviderID is the canonical provider key used across all adapters.
+const GatewayProviderID = gatewayProviderID
+
 // ProviderEntry is a generic provider record. Adapters may massage further.
 type ProviderEntry = map[string]any
 
@@ -161,7 +164,6 @@ func ProvidersAsMap(p *canonical.Profile) map[string]any {
 	return out
 }
 
-
 // KiloModelString returns the "providerID/modelID" string used by kilo/opencode.
 func KiloModelString(p *canonical.Profile) string {
 	if p.Gateway.DefaultModel == "" {

internal/adapter/common/io.go

@@ -40,18 +40,51 @@ func DirExists(path string) bool {
 	return DirExistsFS(fsx.OS(), path)
 }
 
-var (
-	blockComment = regexp.MustCompile(`(?s)/\*.*?\*/`)
-	lineComment  = regexp.MustCompile(`(?m)//[^\n]*`)
-)
+var trailingComma = regexp.MustCompile(`,(\s*[}\]])`)
 
-// StripJSONComments is a naive JSONC -> JSON stripper. It does not understand
-// strings containing // or /* and is therefore only safe for hand-edited
-// config files that don't put comment markers inside string literals.
+// StripJSONComments converts JSONC to standard JSON by:
+//   - removing // line comments (only outside string literals)
+//   - removing /* */ block comments (only outside string literals)
+//   - removing trailing commas before } or ]
+//
+// It is string-aware so it won't mangle // inside URL values like "https://...".
 func StripJSONComments(s string) string {
-	s = blockComment.ReplaceAllString(s, "")
-	s = lineComment.ReplaceAllString(s, "")
-	return strings.TrimSpace(s)
+	result := make([]byte, 0, len(s))
+	i, n := 0, len(s)
+	for i < n {
+		switch {
+		case s[i] == '"': // string literal — copy verbatim including escape sequences
+			result = append(result, s[i])
+			i++
+			for i < n {
+				c := s[i]
+				result = append(result, c)
+				i++
+				if c == '\\' && i < n {
+					result = append(result, s[i])
+					i++
+				} else if c == '"' {
+					break
+				}
+			}
+		case i+1 < n && s[i] == '/' && s[i+1] == '*': // /* block comment */
+			i += 2
+			for i+1 < n && (s[i] != '*' || s[i+1] != '/') {
+				i++
+			}
+			i += 2
+		case i+1 < n && s[i] == '/' && s[i+1] == '/': // // line comment
+			i += 2
+			for i < n && s[i] != '\n' {
+				i++
+			}
+		default:
+			result = append(result, s[i])
+			i++
+		}
+	}
+	out := trailingComma.ReplaceAllString(string(result), "$1")
+	return strings.TrimSpace(out)
 }
 
 // ImportMCPFromJSONFileFS reads a JSON file from fs and extracts an MCP server

internal/adapter/common/mcp.go

@@ -12,7 +12,7 @@ const (
 	MCPCrushStyle
 	// MCPOpencodeStyle: kilo + opencode shape — type: local|remote, command as []string.
 	MCPOpencodeStyle
-	// MCPZedStyle: zed context_servers — {enabled, source, command, args} or {enabled, url}.
+	// MCPZedStyle: zed context_servers — {enabled, command, args} or {enabled, url}.
 	MCPZedStyle
 )
 
@@ -94,11 +94,12 @@ func mcpEntry(s canonical.MCPServer, style MCPStyle) map[string]any {
 		}
 		e["enabled"] = true
 	case MCPZedStyle:
-		e["enabled"] = true
+		// Do NOT emit "enabled" — Zed 1.3.x has a serde flatten+deny_unknown_fields
+		// bug where outer-struct fields bleed into the untagged enum variants and
+		// fail all of them. Omitting "enabled" defaults to true.
 		if s.URL != "" {
 			e["url"] = s.URL
 		} else {
-			e["source"] = "custom"
 			if s.Command != "" {
 				e["command"] = s.Command
 			}

internal/adapter/common/mcp_test.go

@@ -89,8 +89,9 @@ func TestBuildMCPMapStyledZedStdio(t *testing.T) {
 	r := reg(canonical.MCPServer{Name: "fp", Command: "/bin/fp", Args: []string{"-x"}})
 	out := BuildMCPMapStyled(r, MCPZedStyle)
 	e := out["fp"].(map[string]any)
-	assert.Equal(t, true, e["enabled"])
-	assert.Equal(t, "custom", e["source"])
+	// Zed 1.3.x serde bug: "enabled" and "source" must NOT be present.
+	assert.NotContains(t, e, "enabled")
+	assert.NotContains(t, e, "source")
 	assert.Equal(t, "/bin/fp", e["command"])
 	assert.Equal(t, []string{"-x"}, e["args"])
 }
@@ -99,7 +100,8 @@ func TestBuildMCPMapStyledZedURL(t *testing.T) {
 	r := reg(canonical.MCPServer{Name: "r", URL: "https://example.com"})
 	out := BuildMCPMapStyled(r, MCPZedStyle)
 	e := out["r"].(map[string]any)
-	assert.Equal(t, true, e["enabled"])
+	// Zed 1.3.x serde bug: "enabled" must NOT be present.
+	assert.NotContains(t, e, "enabled")
 	assert.Equal(t, "https://example.com", e["url"])
 	assert.NotContains(t, e, "source")
 }

internal/adapter/fileset.go

@@ -6,8 +6,12 @@ type File struct {
 	Dest          string
 	SymlinkTarget string
 	Content       []byte
-	Mode          os.FileMode
 	Kind          Kind
+	Mode          os.FileMode
+	// NoMerge skips the 3-way git merge and always writes the rendered content.
+	// Use for files the adapter partially manages via JSON/YAML merge (e.g. live
+	// state files where the adapter already reconciles at the key level).
+	NoMerge bool
 }
 
 type FileSet struct {