docs(agents): record restack queue discipline around slow image workflow

AGENTS.md

@@ -152,3 +152,19 @@ settings or add CODEOWNERS-based merge gates before then.
   reproduce or isolate the platform-specific cause and do not dismiss an unexplained local failure as platform divergence:
   verify the lane-scoped tests plus `typecheck` locally and let exact-head CI
   carry the full suite.
+- Restack queue discipline, verified 2026-09-09 while integrating PRs #567/#565/#559/#562:
+  `patch-validator-image` can be the slowest exact-head lane, so a burst of ordinary restacks can
+  create avoidable queue pressure. Stagger independent restacks when practical, but keep each PR's
+  merge authority exact: a waiting image result blocks only that PR lane, while path-isolated work
+  that consumes no mutable authority from it may continue. Do not merge the waiting lane until its
+  unchanged exact head has application CI, reviewer-ci, Security Scan, and patch-validator-image
+  GREEN. An early application-CI failure should be diagnosed from its actual failed step rather than
+  elapsed time alone. If a branch is stale, start from the live PR head and current protected base,
+  then ordinary/non-force reconverge and re-run the lane evidence; do not use destructive reset,
+  destructive rebase, or force-push to make history appear current.
+- Dependency-bump lanes must re-prove transitive platform bindings, verified 2026-09-09 on PR #569:
+  a minor bump can drop a platform package from `optionalDependencies` while the registry still
+  publishes it (rolldown 1.2 dropped `@rolldown/binding-wasm32-wasi`, breaking the WASI-only
+  patch-validator materialize step). Reproduce the image materialize battery locally, pin the
+  binding explicitly with a lock-version-alignment regression test when the package remains
+  published, and regenerate the lock plus the lockfile change policy in the same lane.

test/agents-session-handoff-contract.test.ts

@@ -21,4 +21,12 @@ describe("cross-session handoff guidance", () => {
     expect(agents).toContain("reproduce or isolate the platform-specific cause");
     expect(agents).toContain("do not dismiss an unexplained local failure as platform divergence");
   });
+
+  it("keeps slow image work lane-scoped without weakening exact-head merge authority", () => {
+    expect(agents).toContain("a waiting image result blocks only that PR lane");
+    expect(agents).toContain("application CI, reviewer-ci, Security Scan, and patch-validator-image");
+    expect(agents).toContain("ordinary/non-force reconverge");
+    expect(agents).toContain("do not use destructive reset");
+    expect(agents).not.toContain("the only required merge gate is the central Security Scan");
+  });
 });