merge: reconcile retained-root metadata and unmount coverage

Integrate 127aa7a with the newer property-specific Host contract from 805323a. Preserve owned role and ARIA checks, callback and Behavior composition, and caller overrides for ordinary metadata. Carry the historical live-buffer unmount assertions into the current render-port revision test. Regression execution was waived; syntax and diff checks passed.

postmortem/2026-09-08-worktree-integration.md

@@ -0,0 +1,29 @@
+# Historical worktree integration
+
+The September 5 benchmark worktrees contain competing repair attempts against
+an earlier ETAF contract. Their changes were reconciled against current main
+on September 8, rather than replacing the newer implementation.
+
+- `127aa7a` preserves every existing root metadata value. Current main's
+  `805323a` already protects owned role and ARIA semantics, composes callbacks
+  and Behaviors, and allows caller values for ordinary metadata. Retain that
+  more precise implementation when reconciling the old attempt.
+- `a206cfd` changes only the old metadata docstring to describe unrestricted
+  caller overrides. Retain the current docstring because owned semantic
+  conflicts are now rejected explicitly.
+- The retained-root fixture's instance-scoping test is already present in
+  `tests/etaf-component-frontends-tests.el`. Its old role-override expectation
+  conflicts with the current owned-role contract and is superseded by the
+  existing rejection assertion.
+- The three v1 unmount test attempts exercise the same lifecycle outcome.
+  Production no longer exposes the v1 fallback. Their live-buffer, unmounted,
+  zero-revision assertions are carried into the current render-port revision
+  contract test.
+- The metadata baseline deliberately rejects every duplicate metadata key;
+  that blanket rule is superseded by the current property-specific policy.
+- The missing-revision baseline deletes an old v1 test. Both that test and the
+  v1 production route have already been removed by the current SPI boundary.
+
+The historical worktrees remain as evidence. They are not runtime dependencies.
+Regression execution was explicitly waived for this integration; static checks
+do not establish fresh behavioral or performance acceptance.

tests/etaf-render-port-tests.el

@@ -497,7 +497,11 @@
             (should-error (etaf-render-port-revision buffer) :type 'error))
           (cl-letf (((symbol-function 'ebox-surface-buffer-revision)
                      (lambda (_buffer) 0)))
-            (should-error (etaf-render-port-revision buffer) :type 'error)))
+            (should-error (etaf-render-port-revision buffer) :type 'error))
+          (etaf-render-port-unmount buffer)
+          (should (buffer-live-p buffer))
+          (should-not (etaf-render-port-mounted-p buffer))
+          (should (zerop (etaf-render-port-revision buffer))))
       (when (and (buffer-live-p buffer)
                  (ebox-surface-buffer-mounted-p buffer))
         (ebox-unmount-buffer buffer))