Return a clear error for missing owner/repo/issue_number in the copilot assignment tools (#3221)

assign_copilot_to_issue and assign_copilot_to_issue_with_intent decode owner,
repo and issue_number with mapstructure.WeakDecode, which zero-fills a missing
value instead of erroring. A missing required arg then reached the GraphQL query
and surfaced as a confusing "failed to get suggested actors: Could not resolve
to a Repository" error. Reject the zero values after decoding, matching the
is_suggestion and rationale/confidence checks in the same handlers, so the caller
gets "missing required parameter: <name>". Adds table tests for the missing cases.

Co-authored-by: Justin Willhite <5132924+thejdubb02@users.noreply.github.com>

Author: thejdubb02

pkg/github/copilot.go

@@ -214,6 +214,19 @@ func AssignCopilotToIssue(t translations.TranslationHelperFunc) inventory.Server
 				return utils.NewToolResultError(err.Error()), nil, nil
 			}
 
+			// owner, repo and issue_number are required, but WeakDecode zero-fills a
+			// missing value, so a missing arg reached the query as a confusing
+			// "Could not resolve to a Repository" error. Reject the zero values.
+			if params.Owner == "" {
+				return utils.NewToolResultError("missing required parameter: owner"), nil, nil
+			}
+			if params.Repo == "" {
+				return utils.NewToolResultError("missing required parameter: repo"), nil, nil
+			}
+			if params.IssueNumber == 0 {
+				return utils.NewToolResultError("missing required parameter: issue_number"), nil, nil
+			}
+
 			client, err := deps.GetGQLClient(ctx)
 			if err != nil {
 				return nil, nil, fmt.Errorf("failed to get GitHub client: %w", err)
@@ -588,6 +601,19 @@ func AssignCopilotToIssueWithIntent(t translations.TranslationHelperFunc) invent
 				return utils.NewToolResultError(err.Error()), nil, nil
 			}
 
+			// owner, repo and issue_number are required, but WeakDecode zero-fills a
+			// missing value, so reject the zero values (as with rationale/confidence
+			// below) before they reach the query as a confusing repository error.
+			if params.Owner == "" {
+				return utils.NewToolResultError("missing required parameter: owner"), nil, nil
+			}
+			if params.Repo == "" {
+				return utils.NewToolResultError("missing required parameter: repo"), nil, nil
+			}
+			if params.IssueNumber == 0 {
+				return utils.NewToolResultError("missing required parameter: issue_number"), nil, nil
+			}
+
 			// Validate rationale length (rune count, matching the granular assignee tools).
 			rationale := strings.TrimSpace(params.Rationale)
 			if rationale == "" {

pkg/github/copilot_test.go

@@ -59,6 +59,36 @@ func TestAssignCopilotToIssue(t *testing.T) {
 		expectToolError    bool
 		expectedToolErrMsg string
 	}{
+		{
+			name: "missing owner is rejected",
+			requestArgs: map[string]any{
+				"repo":         "repo",
+				"issue_number": float64(123),
+			},
+			mockedClient:       githubv4mock.NewMockedHTTPClient(),
+			expectToolError:    true,
+			expectedToolErrMsg: "missing required parameter: owner",
+		},
+		{
+			name: "missing repo is rejected",
+			requestArgs: map[string]any{
+				"owner":        "owner",
+				"issue_number": float64(123),
+			},
+			mockedClient:       githubv4mock.NewMockedHTTPClient(),
+			expectToolError:    true,
+			expectedToolErrMsg: "missing required parameter: repo",
+		},
+		{
+			name: "missing issue_number is rejected",
+			requestArgs: map[string]any{
+				"owner": "owner",
+				"repo":  "repo",
+			},
+			mockedClient:       githubv4mock.NewMockedHTTPClient(),
+			expectToolError:    true,
+			expectedToolErrMsg: "missing required parameter: issue_number",
+		},
 		{
 			name: "successful assignment when there are no existing assignees",
 			requestArgs: map[string]any{
@@ -1228,6 +1258,19 @@ func TestAssignCopilotToIssueWithIntent(t *testing.T) {
 		expectedToolErrMsg string
 		expectSuggestion   bool
 	}{
+		{
+			name: "missing owner is rejected",
+			requestArgs: map[string]any{
+				"repo":          "repo",
+				"issue_number":  float64(123),
+				"rationale":     "Well-scoped task.",
+				"confidence":    "HIGH",
+				"is_suggestion": false,
+			},
+			mockedClient:       githubv4mock.NewMockedHTTPClient(),
+			expectToolError:    true,
+			expectedToolErrMsg: "missing required parameter: owner",
+		},
 		{
 			name: "direct assignment with rationale and confidence preserves existing assignees",
 			requestArgs: map[string]any{