Promote develop to main: repo-wide bot-node-id cold-start fallback

.github/copilot-instructions.md

@@ -56,7 +56,28 @@ mutation($pr: ID!, $bot: ID!) {
 }' -F pr="$PR_NODE" -F bot="$BOT_ID"
 ```
 
-The bot node id is read from an existing Copilot **formal** review (`pullRequest.reviews`), so step 1 needs at least one prior formal review on the PR - the auto-review-on-open normally supplies the first one (it may have **no inline comments**; that still counts, and its bot node id is still readable). Poll for it (give auto-review-on-open a few minutes) before deciding it is missing. If Copilot posted **only an issue comment** and no formal review, the head is covered but `reviews` yields no bot node id - read the id from the Copilot issue comment's author by querying the PR's issue comments in GraphQL (`pullRequest.comments` -> author `... on Bot { id }`), or request `Copilot` once through the GitHub PR UI to produce a formal review. Manual UI seeding is the fallback specifically when no formal review exists to read the id from; then use the mutation for every subsequent re-request.
+The bot node id is read from an existing Copilot **formal** review (`pullRequest.reviews`), so step 1 needs at least one prior formal review on the PR - the auto-review-on-open normally supplies the first one (it may have **no inline comments**; that still counts, and its bot node id is still readable). Poll for it (give auto-review-on-open a few minutes) before deciding it is missing.
+
+**Cold start (round 1 not yet landed): read the id repo-wide, not from this PR.** The Copilot reviewer's bot node id is the reviewer bot *account's* node id and is **stable across every PR in the repo**. So a freshly opened PR that has neither a formal review nor an issue comment yet does **not** need UI seeding to bootstrap the id - read it from any prior Copilot review anywhere in the repo, then feed it into the `requestReviews` mutation to drive round 1. Query the **most recent** PRs (`first: 20` with an explicit newest-first order; plain `last: 20` returns the *oldest* PRs, which may predate Copilot on the repo), and **guard for an empty result** - an empty `$BOT_ID` means none of the sampled PRs carry a Copilot review. Widen the window (raise the count or paginate) before concluding the repo has never had one and falling back to UI seeding; never feed an empty id into the mutation:
+
+```sh
+BOT_ID=$(gh api graphql -f query='
+{
+  repository(owner: "<owner>", name: "<repo>") {
+    pullRequests(first: 20, orderBy: { field: CREATED_AT, direction: DESC }) {
+      nodes { reviews(first: 20) { nodes { author { __typename login ... on Bot { id } } } } }
+    }
+  }
+}' --jq '[.data.repository.pullRequests.nodes[].reviews.nodes[]
+          | select(.author.login == "copilot-pull-request-reviewer")
+          | .author.id] | first // empty')
+if [ -z "$BOT_ID" ]; then
+  echo "no Copilot review in the 20 most recent PRs - widen the window, else fall back to UI seeding" >&2
+  return 1 2>/dev/null || exit 1   # stop; do NOT call requestReviews with an empty id
+fi
+```
+
+If Copilot posted **only an issue comment** on this PR and no formal review, you can instead read the id from that comment's author (`pullRequest.comments` -> author `... on Bot { id }`). Manual UI seeding is the last resort - needed only for a repo that has **never** had a Copilot review, so no prior id exists anywhere to read; then use the mutation for every subsequent re-request.
 
 **Do NOT post `@Copilot review` as a PR comment.** That comment triggers the Copilot *coding agent* (`copilot-swe-agent[bot]`), which makes code changes rather than posting a review.