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_test.go

@@ -0,0 +1,39 @@
+package gitea_test
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSearchCode(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "/api/v1/repos/mathias/infra/search", r.URL.Path)
+		assert.Equal(t, "SearchCode", r.URL.Query().Get("q"))
+		assert.Equal(t, "code", r.URL.Query().Get("type"))
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{
+			"data":[{
+				"path":"internal/gitea/code_search.go",
+				"snippet":"func (c *Client) SearchCode",
+				"html_url":"http://gitea.example.com/mathias/infra/src/branch/main/internal/gitea/code_search.go",
+				"score":2.5
+			}],
+			"ok":true
+		}`))
+	}))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	hits, err := c.SearchCode(context.Background(), "mathias", "infra", "SearchCode", 1, 30)
+	require.NoError(t, err)
+	require.Len(t, hits, 1)
+	assert.Equal(t, "internal/gitea/code_search.go", hits[0].Path)
+	assert.Equal(t, "func (c *Client) SearchCode", hits[0].Snippet)
+	assert.InDelta(t, 2.5, hits[0].Score, 0.001)
+}