feat: slim tool responses (#141)

Reduce token usage by slimming tool responses. Instead of returning full Gitea SDK objects (with nested user/repo objects, avatars, permissions, etc.), each operation now has a colocated `slim.go` that extracts only the fields an LLM needs. List endpoints return even fewer fields than single-item endpoints.

Other changes:
- Add `params` helpers to DRY parameter extraction across 40+ handlers
- Remove `{"Result": ...}` wrapper for flatter responses
- Reduce default pageSize from 100 to 30

Fixes: https://gitea.com/gitea/gitea-mcp/issues/128

*Created by Claude on behalf of @silverwind*

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/141
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

operation/issue/slim.go

@@ -0,0 +1,116 @@
+package issue
+
+import (
+	gitea_sdk "code.gitea.io/sdk/gitea"
+)
+
+func userLogin(u *gitea_sdk.User) string {
+	if u == nil {
+		return ""
+	}
+	return u.UserName
+}
+
+func userLogins(users []*gitea_sdk.User) []string {
+	if len(users) == 0 {
+		return nil
+	}
+	out := make([]string, 0, len(users))
+	for _, u := range users {
+		if u != nil {
+			out = append(out, u.UserName)
+		}
+	}
+	return out
+}
+
+func labelNames(labels []*gitea_sdk.Label) []string {
+	if len(labels) == 0 {
+		return nil
+	}
+	out := make([]string, 0, len(labels))
+	for _, l := range labels {
+		if l != nil {
+			out = append(out, l.Name)
+		}
+	}
+	return out
+}
+
+func slimIssue(i *gitea_sdk.Issue) map[string]any {
+	if i == nil {
+		return nil
+	}
+	m := map[string]any{
+		"number":     i.Index,
+		"title":      i.Title,
+		"body":       i.Body,
+		"state":      i.State,
+		"html_url":   i.HTMLURL,
+		"user":       userLogin(i.Poster),
+		"labels":     labelNames(i.Labels),
+		"comments":   i.Comments,
+		"created_at": i.Created,
+		"updated_at": i.Updated,
+		"closed_at":  i.Closed,
+	}
+	if len(i.Assignees) > 0 {
+		m["assignees"] = userLogins(i.Assignees)
+	}
+	if i.Milestone != nil {
+		m["milestone"] = map[string]any{
+			"id":    i.Milestone.ID,
+			"title": i.Milestone.Title,
+		}
+	}
+	if i.PullRequest != nil {
+		m["is_pull"] = true
+	}
+	return m
+}
+
+func slimIssues(issues []*gitea_sdk.Issue) []map[string]any {
+	out := make([]map[string]any, 0, len(issues))
+	for _, i := range issues {
+		if i == nil {
+			continue
+		}
+		m := map[string]any{
+			"number":     i.Index,
+			"title":      i.Title,
+			"state":      i.State,
+			"html_url":   i.HTMLURL,
+			"user":       userLogin(i.Poster),
+			"comments":   i.Comments,
+			"created_at": i.Created,
+			"updated_at": i.Updated,
+		}
+		if len(i.Labels) > 0 {
+			m["labels"] = labelNames(i.Labels)
+		}
+		out = append(out, m)
+	}
+	return out
+}
+
+func slimComment(c *gitea_sdk.Comment) map[string]any {
+	if c == nil {
+		return nil
+	}
+	return map[string]any{
+		"id":         c.ID,
+		"body":       c.Body,
+		"user":       userLogin(c.Poster),
+		"html_url":   c.HTMLURL,
+		"created_at": c.Created,
+		"updated_at": c.Updated,
+	}
+}
+
+func slimComments(comments []*gitea_sdk.Comment) []map[string]any {
+	out := make([]map[string]any, 0, len(comments))
+	for _, c := range comments {
+		out = append(out, slimComment(c))
+	}
+	return out
+}