audit: cycle copy-close tidy — reconcile spec to shipped structure

Cycle-close audit for the case-page copy+close cycle (spec 0002, plan
0003, feat 0308245). Architect drift review + scripts/check.sh.

Regression gate (scripts/check.sh): exit 0 — 0 failures across 19
stages (common/server/clients-desktop/experiments fmt+clippy+build+test,
wearos assembleDebug+lintDebug+testDebugUnitTest), 74s. The single
`wearos :: lintDebug` WARN is pre-existing and untouched by this
frontend-only cycle; not introduced here, carried forward.

Architect findings and resolution:
- [high] template emits two separate close forms, not the spec's single
  #copy-close-form with a has_document label switch. Resolved as a SPEC
  defect, not a code defect: the spec's single-form snippet was
  infeasible — #doc-body exists only in the has-document match arm, so a
  form anchored after it can never serve the documentless case, and it
  must precede the copy <script> to be bound. The shipped two-form split
  is canonical; spec 0002 §Concrete code shapes + §Data flow reconciled
  to it (this commit).
- [high] the spec's `if (!getElementById("doc-body")) return` guard is
  absent from the shipped handler. Not a defect: the no-document form
  carries no id, so the handler (which binds #copy-close-form) never
  attaches to it — the guard is structurally unnecessary. Spec script
  block + prose updated to state this mechanism.
- [medium] the documentless form's distinctness was unpinned. Added an
  assertion to case_page_empty_case_shows_placeholder that the empty
  case renders no #copy-close-form (it is the bare close form).
- [low] plan counter 0003 vs spec counter 0002: not drift — the naming
  policy is per-directory counters (stable_per_directory_4digit over
  [docs/specs, docs/plans]); independent sequences are expected.
- [note] deferred case-list half of #14 leaves a coherent state
  (refs #14, my_cases.html untouched). No drift.

Recommendation: carry-on. No fix iteration needed; the high items were
spec-vs-code reconciliation (docs) and a test guard, both done here.

refs #14

server/tests/case_page_test.rs

@@ -299,6 +299,13 @@ async fn case_page_empty_case_shows_placeholder() {
         body.contains(r#">Schließen</button>"#),
         "documentless open case must offer a bare Schließen button"
     );
+    // The documentless close is the BARE form, not the copy-close form:
+    // with no document there is nothing to copy, so it must not bind the
+    // clipboard-gated submit handler.
+    assert!(
+        !body.contains(r#"id="copy-close-form""#),
+        "documentless open case must use the bare close form, not the copy-close form"
+    );
 }
 
 #[tokio::test]