feat(connector): add search and fetch tools for ChatGPT connectors

Add a new "connector" domain exposing exactly-named "search" and "fetch"
MCP tools for ChatGPT-style connector compatibility (gitea#84). search
looks up repositories via the existing SearchRepos SDK call, optionally
resolving an owner/org name to an owner ID, and returns concise entries
(id, name, url, html_url). fetch reuses GetContents to read a file and
decodes its base64 content, returning path, sha, size, encoding and the
decoded content. Registers connector.Tool in operation.go and documents
the two tools in all three README tables.

Co-Authored-By: Codet <codet@commitgo.dev> (GPT-5-Codex)

operation/connector/slim.go

@@ -0,0 +1,29 @@
+package connector
+
+import (
+	gitea_sdk "gitea.dev/sdk"
+)
+
+// slimSearchResult is the concise entry shape ChatGPT-style connectors
+// expect from search: an id, a title, and a url to fetch it by.
+func slimSearchResult(r *gitea_sdk.Repository) map[string]any {
+	if r == nil {
+		return nil
+	}
+	return map[string]any{
+		"id":          r.ID,
+		"name":        r.Name,
+		"full_name":   r.FullName,
+		"description": r.Description,
+		"url":         r.HTMLURL,
+		"html_url":    r.HTMLURL,
+	}
+}
+
+func slimSearchResults(repos []*gitea_sdk.Repository) []map[string]any {
+	out := make([]map[string]any, 0, len(repos))
+	for _, r := range repos {
+		out = append(out, slimSearchResult(r))
+	}
+	return out
+}