Implements #60.

- Add ParsePersonaBytes() for parsing personas from byte data
- Add LoadRepoPersonas() to fetch personas from repo via Gitea API
- Add MergePersonas() to combine built-in and repo personas
- Add GetBuiltinPersonasMap() helper
- Update main.go to load repo personas first, fall back to built-in
- Add giteaClientAdapter to bridge gitea.Client to review.GiteaClient

When --persona is specified, the bot now:
1. Attempts to fetch personas from .review-bot/personas/*.yaml
2. If the named persona exists in the repo, uses it
3. Otherwise falls back to built-in personas

This allows repos to define domain-specific personas (e.g., trading
experts for gargoyle, crypto experts for kms-lite) without modifying
the review-bot codebase.

@@ -199,0 +182,4 @@
+		if err != nil {
+			slog.Warn("could not load repo personas", "repo", owner+"/"+repoName, "error", err)
+			// Continue with built-in personas only
+		}

@@ -0,0 +130,4 @@
+// isNotFoundError checks if an error represents a 404 response.
+// This is a string-based heuristic since we don't have access to gitea.APIError here.
+func isNotFoundError(err error) bool {
+	if err == nil {

@@ -0,0 +15,4 @@
+		wantName   string
+		wantErr    string
+	}{
+		{

@@ -227,0 +228,4 @@
+// This is useful for parsing personas fetched from external sources (e.g., Gitea API)
+// without requiring filesystem access. Format is detected by source extension.
+func ParsePersonaBytes(data []byte, source string) (*Persona, error) {
+	return parsePersona(data, source)

@@ -0,0 +61,4 @@
+			slog.Warn("could not fetch repo persona file",
+				"file", entry.Path,
+				"repo", owner+"/"+repo,
+				"error", err)

@@ -0,0 +118,4 @@
+		}
+		result[name] = p
+	}
+	return result

@@ -0,0 +60,4 @@
+		if err != nil {
+			slog.Warn("could not fetch repo persona file",
+				"file", entry.Path,
+				"repo", owner+"/"+repo,

@@ -0,0 +101,4 @@
+			slog.Debug("repo persona overrides built-in", "name", name)
+		}
+		result[name] = p
+	}

@@ -199,0 +180,4 @@
+		// Try loading from repo first, then fall back to built-in
+		repoPersonas, err := review.LoadRepoPersonas(ctx, newGiteaClientAdapter(giteaClient), owner, repoName)
+		if err != nil {
+			slog.Warn("could not load repo personas", "repo", owner+"/"+repoName, "error", err)

@@ -786,0 +822,4 @@
+	return result, nil
+}
+
+func (a *giteaClientAdapter) GetFileContent(ctx context.Context, owner, repo, filepath string) (string, error) {

@@ -0,0 +10,4 @@
+const RepoPersonaPath = ".review-bot/personas"
+
+// GiteaClient defines the subset of gitea.Client methods needed for loading repo personas.
+// This interface allows for easier testing and decouples the review package from gitea.

@@ -0,0 +125,4 @@
+func isYAMLFile(name string) bool {
+	lower := strings.ToLower(name)
+	return strings.HasSuffix(lower, ".yaml") || strings.HasSuffix(lower, ".yml")
+}

@@ -0,0 +10,4 @@
+func TestParsePersonaBytes(t *testing.T) {
+	tests := []struct {
+		name       string
+		data       string

@@ -0,0 +48,4 @@
+	}
+
+	for _, entry := range entries {
+		if entry.Type != "file" {

@@ -0,0 +106,4 @@
+	return result
+}
+
+// GetBuiltinPersonasMap returns all built-in personas as a map keyed by name.

@@ -0,0 +42,4 @@
+		return nil, err
+	}
+
+	if len(entries) == 0 {

@@ -0,0 +51,4 @@
+		if entry.Type != "file" {
+			continue
+		}
+		// Only process YAML files

@@ -81,4 +81,3 @@
 
-	flag.Parse()
 	flag.Parse()
 

@@ -199,0 +180,4 @@
+		repoPersonas, err := review.LoadRepoPersonas(ctx, newGiteaClientAdapter(giteaClient), owner, repoName)
+		if err != nil {
+			slog.Warn("could not load repo personas", "repo", owner+"/"+repoName, "error", err)
+			// Continue with built-in personas only.

@@ -0,0 +77,4 @@
+		}
+
+		persona, err := ParsePersonaBytes([]byte(content), entry.Path)
+		if err != nil {

@@ -0,0 +127,4 @@
+			slog.Warn("could not load built-in persona", "name", name, "error", err)
+			continue
+		}
+		result[name] = p

@@ -0,0 +13,4 @@
+		data       string
+		source     string
+		wantName   string
+		wantErr    string

@@ -196,6 +173,43 @@ func main() {
 	ctx, cancel := context.WithTimeout(context.Background(), overallTimeout)

@@ -0,0 +107,4 @@
+	}
+
+	// Overlay repo personas (override on collision)
+	for name, p := range repo {

@@ -0,0 +113,4 @@
+		}
+		result[name] = p
+	}
+

@@ -79,7 +79,6 @@ func main() {
 	aicoreAPIURL := flag.String("aicore-api-url", envOrDefault("AICORE_API_URL", ""), "SAP AI Core API URL (for provider=aicore)")
 	aicoreResourceGroup := flag.String("aicore-resource-group", envOrDefault("AICORE_RESOURCE_GROUP", "default"), "SAP AI Core resource group (for provider=aicore)")
 

@@ -199,0 +182,4 @@
+			slog.Warn("could not load repo personas", "repo", owner+"/"+repoName, "error", err)
+			// Continue with built-in personas only.
+			// NOTE: repoPersonas is nil here, but map indexing on a nil map is safe in Go
+			// (returns the zero value), so the fallback to built-in below works correctly.

@@ -0,0 +83,4 @@
+				"repo", owner+"/"+repo,
+				"error", err)
+			continue
+		}

@@ -0,0 +144,4 @@
+// contain "not found" in their message.
+func isNotFoundError(err error) bool {
+	if err == nil {
+		return false

@@ -0,0 +16,4 @@
+		wantErr    string
+	}{
+		{
+			name: "valid yaml",

@@ -0,0 +67,4 @@
+		}
+
+		// Enforce size limit before parsing to prevent resource exhaustion
+		if len(content) > MaxPersonaFileSize {

@@ -0,0 +142,4 @@
+// This uses a specific "HTTP 404" substring match rather than a generic "not found"
+// match to avoid masking authentication failures or transport errors that might
+// contain "not found" in their message.
+func isNotFoundError(err error) bool {

@@ -0,0 +138,4 @@
+	return strings.HasSuffix(lower, ".yaml") || strings.HasSuffix(lower, ".yml")
+}
+
+// isNotFoundError checks if an error represents a 404 response.

@@ -0,0 +48,4 @@
+		return result, nil
+	}
+
+	for _, entry := range entries {