Implement GitHub suggestion format instructions (#79)

* implement github suggestion format instructions

add instructions for agents to use github's suggestion format (```suggestion blocks) when providing code suggestions in comments. this enables one-click apply for suggested changes.

updated:
- action/mcp/review.ts: added suggestion format guidance to create_pull_request_review tool description and comment body parameter
- action/mcp/comment.ts: added suggestion format guidance to all comment tools with clarification that suggestions only work on pr line-level review comments
- action/modes.ts: added detailed example in review mode and reminder in address reviews mode

fixes #70

* Address PR review feedback

- Remove suggestion format guidance from report_progress (not applicable)
- De-duplicate description across Comment, EditComment, ReplyToReviewComment
- Drop outer fence in suggestion format example
- Clarify that suggestions only work for self-contained changes
- Remove useless example comment from review tool description

---------

Co-authored-by: pullfrog <team@pullfrog.com>

mcp/comment.ts

@@ -77,6 +77,9 @@ async function buildCommentFooter({
   return buildPullfrogFooter(footerParams);
 }
 
+const SUGGESTION_FORMAT_DESCRIPTION =
+  "when suggesting code changes, use GitHub's suggestion format with ```suggestion blocks to enable one-click apply (e.g., 'you could do this\\n```suggestion\\nsuggested code here\\n```'). note: suggestions only work on pull request line-level review comments, not on issue/PR-level comments.";
+
 function buildImplementPlanLink(
   owner: string,
   repo: string,
@@ -99,7 +102,7 @@ async function addFooter(
 
 export const Comment = type({
   issueNumber: type.number.describe("the issue number to comment on"),
-  body: type.string.describe("the comment body content"),
+  body: type.string.describe(`the comment body content. ${SUGGESTION_FORMAT_DESCRIPTION}`),
 });
 
 export function CreateCommentTool(ctx: ToolContext) {
@@ -130,7 +133,7 @@ export function CreateCommentTool(ctx: ToolContext) {
 
 export const EditComment = type({
   commentId: type.number.describe("the ID of the comment to edit"),
-  body: type.string.describe("the new comment body content"),
+  body: type.string.describe(`the new comment body content. ${SUGGESTION_FORMAT_DESCRIPTION}`),
 });
 
 export function EditCommentTool(ctx: ToolContext) {
@@ -472,7 +475,7 @@ export const ReplyToReviewComment = type({
   pull_number: type.number.describe("the pull request number"),
   comment_id: type.number.describe("the ID of the review comment to reply to"),
   body: type.string.describe(
-    "extremely brief reply (1 sentence max) explaining what was fixed, e.g. 'Fixed by renaming to X' or 'Added null check'"
+    `extremely brief reply (1 sentence max) explaining what was fixed, e.g. 'Fixed by renaming to X' or 'Added null check'. ${SUGGESTION_FORMAT_DESCRIPTION}`
   ),
 });