add Summarize mode for updatable PR summary comments (#470)

* add Summarize mode for updatable PR summary comments

Introduces a Summarize mode that manages a single summary comment per PR,
updated in place on subsequent pushes. Mirrors the Plan/PlanEdit pattern:
API endpoint for existing-comment lookup at select_mode time, node ID
tracking on WorkflowRun, and SummaryUpdate guidance for edits.

Also fixes summary format instructions: Before/After uses inline <br/>
to avoid double line breaks, metadata line placed after key changes,
SHA-256 anchor instructions strengthened against fabrication.

Made-with: Cursor

* fix pre-existing lint error in checkout.ts

Made-with: Cursor

* fix dead restricted param in deepenForBeforeSha

GitAuthOptions dropped the restricted field in the ASKPASS refactor (#478)
but deepenForBeforeSha (#471) still passed it. Remove the field and the
now-unused shell param from DeepenForBeforeShaParams.

Made-with: Cursor

post

@@ -41256,8 +41256,8 @@ var LEAPING_INTO_ACTION_PREFIX = "Leaping into action";
 var Comment = type({
   issueNumber: type.number.describe("the issue number to comment on"),
   body: type.string.describe("the comment body content"),
-  type: type.enumerated("Plan", "Comment").describe(
-    "Plan: record this comment as the plan for this run (use report_progress for progress/plan updates on the current run). Comment: regular comment (default)."
+  type: type.enumerated("Plan", "Summary", "Comment").describe(
+    "Plan: record as the plan for this run. Summary: record as the PR summary comment (one per PR, updated in place). Comment: regular comment (default)."
   ).optional()
 });
 var EditComment = type({