Implement the remaining vcs.Client interface methods for github.Client:

Reviewer:
- PostReview: POST /repos/{owner}/{repo}/pulls/{number}/reviews
- ListReviews: GET /repos/{owner}/{repo}/pulls/{number}/reviews
  with state translation (CHANGES_REQUESTED → REQUEST_CHANGES, etc.)
- DeleteReview: DELETE /repos/{owner}/{repo}/pulls/{number}/reviews/{id}
  Returns ErrCannotDeleteSubmittedReview on 422
- DismissReview: PUT /repos/{owner}/{repo}/pulls/{number}/reviews/{id}/dismissals

Identity:
- GetAuthenticatedUser: GET /user

Infrastructure:
- Add doRequestWithBody helper for POST/PUT/DELETE with JSON bodies
- Update conformance_test.go: var _ vcs.Client = (*github.Client)(nil)

All unit tests pass including error cases (401, 404, 422, malformed).

@@ -342,3 +343,113 @@ func (c *Client) handleResponse(resp *http.Response, maxRespBytes int, maxErrByt
 func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
 	return c.doRequest(ctx, http.MethodGet, reqURL, "")
 }
+

@@ -0,0 +59,4 @@
+	case "COMMENTED":
+		return "COMMENT"
+	case "DISMISSED":
+		return "DISMISSED"

@@ -0,0 +107,4 @@
+
+	var resp reviewResponse
+	if err := json.Unmarshal(body, &resp); err != nil {
+		return nil, fmt.Errorf("parse review response: %w", err)

@@ -0,0 +377,4 @@
+			t.Errorf("translateGitHubReviewState(%q) = %q, want %q", tt.input, got, tt.expected)
+		}
+	}
+}

@@ -342,3 +343,113 @@ func (c *Client) handleResponse(resp *http.Response, maxRespBytes int, maxErrByt
 func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
 	return c.doRequest(ctx, http.MethodGet, reqURL, "")
 }
+

@@ -0,0 +110,4 @@
+		return nil, fmt.Errorf("parse review response: %w", err)
+	}
+
+	return &vcs.Review{

@@ -0,0 +147,4 @@
+	}
+	return reviews, nil
+}
+

@@ -0,0 +357,4 @@
+	}
+}
+
+// --- State translation tests ---

@@ -0,0 +53,4 @@
+// canonical vcs.Review.State value.
+func translateGitHubReviewState(state string) string {
+	switch state {
+	case "CHANGES_REQUESTED":

@@ -0,0 +80,4 @@
+	// Populate CommitID from the first comment if available.
+	// All comments in a single review share the same commit_id.
+	for _, comment := range req.Comments {
+		if comment.CommitID != "" {

@@ -0,0 +378,4 @@
+			t.Errorf("translateGitHubReviewState(%q) = %q, want %q", tt.input, got, tt.expected)
+		}
+	}
+}

@@ -197,2 +196,2 @@
-// Transport errors (network failures, context cancellation) are not retried.
-func (c *Client) doRequest(ctx context.Context, method, reqURL string, accept string) ([]byte, error) {
+// requestOptions holds per-request configuration for doRequestCore.
+type requestOptions struct {

@@ -0,0 +99,4 @@
+		return nil, fmt.Errorf("marshal review request: %w", err)
+	}
+
+	body, err := c.doRequestWithBody(ctx, http.MethodPost, reqURL, data)

@@ -0,0 +1,46 @@
+package github

@@ -0,0 +54,4 @@
+func translateGitHubReviewState(state string) string {
+	switch state {
+	case "CHANGES_REQUESTED":
+		return "REQUEST_CHANGES"

@@ -0,0 +77,4 @@
+		Body:  req.Body,
+		Event: string(req.Event),
+	}
+

@@ -0,0 +10,4 @@
+	"strings"
+	"testing"
+	"time"
+

@@ -345,0 +383,4 @@
+		opts.extraHeaders = map[string]string{"Content-Type": "application/json"}
+	}
+	return c.doRequestCore(ctx, method, reqURL, opts)
+}

@@ -0,0 +94,4 @@
+			Path:     comment.Path,
+			Position: comment.Position,
+			Body:     comment.Body,
+		})

@@ -0,0 +11,4 @@
+	"testing"
+	"time"
+
+	"gitea.weiker.me/rodin/review-bot/vcs"

@@ -0,0 +351,4 @@
+
+	err := c.DismissReview(context.Background(), "owner", "repo", 5, 10, "dismiss")
+	if err == nil {
+		t.Fatal("expected error for 401")

@@ -0,0 +20,4 @@
+		}
+		json.NewEncoder(w).Encode(map[string]string{"login": "review-bot"})
+	})
+

@@ -0,0 +165,4 @@
+	return reviews, nil
+}
+
+// DeleteReview deletes a pull request review.

@@ -0,0 +1,388 @@
+package github

@@ -0,0 +159,4 @@
+			Body:     r.Body,
+			User:     vcs.UserInfo{Login: r.User.Login},
+			State:    translateGitHubReviewState(r.State),
+			CommitID: r.CommitID,

@@ -0,0 +192,4 @@
+	reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews/%d/dismissals",
+		c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number, reviewID)
+
+	payload := dismissReviewRequest{

@@ -0,0 +12,4 @@
+	"gitea.weiker.me/rodin/review-bot/vcs"
+)
+
+// --- PostReview tests ---

@@ -345,0 +380,4 @@
+	var opts requestOptions
+	if reqBody != nil {
+		opts.bodyFn = func() io.Reader { return bytes.NewReader(reqBody) }
+		opts.extraHeaders = map[string]string{"Content-Type": "application/json"}

@@ -0,0 +159,4 @@
+			Body:     r.Body,
+			User:     vcs.UserInfo{Login: r.User.Login},
+			State:    translateGitHubReviewState(r.State),
+			CommitID: r.CommitID,

@@ -0,0 +12,4 @@
+	"gitea.weiker.me/rodin/review-bot/vcs"
+)
+
+// --- PostReview tests ---

@@ -0,0 +192,4 @@
+	reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews/%d/dismissals",
+		c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number, reviewID)
+
+	payload := dismissReviewRequest{

@@ -0,0 +12,4 @@
+	"gitea.weiker.me/rodin/review-bot/vcs"
+)
+
+// --- PostReview tests ---

@@ -0,0 +159,4 @@
+			Body:     r.Body,
+			User:     vcs.UserInfo{Login: r.User.Login},
+			State:    translateGitHubReviewState(r.State),
+			CommitID: r.CommitID,

@@ -0,0 +19,4 @@
+			t.Errorf("unexpected auth header: %s", r.Header.Get("Authorization"))
+		}
+		json.NewEncoder(w).Encode(map[string]string{"login": "review-bot"})
+	})

@@ -0,0 +167,4 @@
+
+// DeleteReview deletes a pull request review.
+// Only PENDING reviews can be deleted; attempting to delete a submitted review
+// (APPROVED, CHANGES_REQUESTED, or COMMENTED per GitHub API naming) returns

@@ -0,0 +35,4 @@
+		if req.Event != "APPROVE" {
+			t.Errorf("expected event APPROVE, got %q", req.Event)
+		}
+		if req.Body != "LGTM" {