chore(copilot-config): reduce review noise (#27084)

.agents/docs/code-review.md

@@ -4,6 +4,11 @@ Reviewing a changeset or PR, your own before submission or a contributor's. The
 (`cpp-guidelines.md`, `sql-guidelines.md`, `cpp-scripts.md`) apply as a checklist to every changed
 line, not as background reading.
 
+- A posted review carries findings only: no summary, no praise. Nothing to report means one line
+  saying so.
+- A finding names what is wrong, why it matters and the fix, on the offending line. Findings are
+  bugs, crashes, lifetime and memory errors, data-integrity problems, injection, and violations of
+  a rule written down in AGENTS.md or `.agents/docs/`; taste no rule covers is not a finding.
 - Review codestyle on every changed line, even when style is not the change's subject. Run both
   linters and report violations as findings: `python apps/codestyle/codestyle-cpp.py` and
   `python apps/codestyle/codestyle-sql.py`.

.github/copilot-instructions.md

@@ -0,0 +1,10 @@
+# Copilot instructions
+
+Follow `AGENTS.md` and the guides it routes to in `.agents/docs/`. For pull request review, follow
+`.agents/docs/code-review.md`.
+
+## Review output
+
+- No overview paragraph, no "Changes" list, no per-file table.
+- Put findings in inline comments on the offending lines, not the review body.
+- With no findings, post one line saying so and nothing else.