feat(tools): code_search (single-repo)

Adds SearchCode to gitea.Client and code_search MCP tool for single-repo
code search via GET /api/v1/repos/{owner}/{repo}/search?type=code.
Fan-out placeholder returns ErrValidation (lands in 7.3).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/gitea/code_search.go

@@ -0,0 +1,43 @@
+package gitea
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/url"
+)
+
+type CodeSearchHit struct {
+	Path    string  `json:"path"`
+	Snippet string  `json:"snippet"`
+	HTMLURL string  `json:"html_url"`
+	Score   float64 `json:"score,omitempty"`
+}
+
+type codeSearchEnvelope struct {
+	Data []CodeSearchHit `json:"data"`
+	OK   bool            `json:"ok"`
+}
+
+func (c *Client) SearchCode(ctx context.Context, owner, repo, q string, page, limit int) ([]CodeSearchHit, error) {
+	if page < 1 {
+		page = 1
+	}
+	if limit < 1 {
+		limit = 30
+	}
+	path := fmt.Sprintf("/api/v1/repos/%s/%s/search?q=%s&type=code&page=%d&limit=%d",
+		owner, repo, url.QueryEscape(q), page, limit)
+	body, status, err := c.GetJSON(ctx, path)
+	if err != nil {
+		return nil, err
+	}
+	if err := MapStatus(status, body); err != nil {
+		return nil, err
+	}
+	var env codeSearchEnvelope
+	if err := json.Unmarshal(body, &env); err != nil {
+		return nil, err
+	}
+	return env.Data, nil
+}