T7.2 - F6/D3: the form gets structure - a section rail, one section open

F6 as amended by D3 (Aug 18): one page, persistent side navigation, sections
collapsible, only the current one open by default, plus Expand all. Tabs were
rejected in D3 because they hide sections a first-time author does not know
exist.

What changed:
- The jump-chip strip (#section-nav, span onclick) is gone. In its place a
  <nav> section rail of real <button> entries, aria-current on the current
  section, 44px tap targets, above the form at 390px and beside it at 1440px.
- Every section heading is now a disclosure <button> with aria-expanded and
  aria-controls. One section open at rest; Expand all (aria-pressed) opens
  everything and is remembered per browser.
- Sections are URL-addressable (?section=, T4.2 machinery) and a deep link to
  a collapsed section expands it. Positional-id fallback removed: a card
  without an id gets a console.error and no rail entry, never an invented
  sec-N id that would ride into shareable URLs and move between visits.
- General Information (1,288px on its own) split into #general-card and
  #assign-card (Assignment & Schedule). The split is presentational: both
  cards are the ONE CR-006 section `general` (WP_SECTION_NODES lists both),
  so wp-sections.js and the SOP wizard are untouched. CR-001's adjacency
  (P6 activity beside due date) is preserved and asserted.
- gotoSection() flushes autosave, which the deleted chips used to do.
- secMakeToggle() preserves every element child of a heading - help tips go
  outside the button, everything else inside the label. The first version
  cleared textContent and destroyed #saved-count, which killed boot one line
  short of wpCreatorReady with the page still visibly rendered.
- BL-013 folded in per the task: the T3.4 focus ring on the rebuilt form.
  frame_check reports outline solid 2px on creator inputs.

Height, measured not asserted: 5,399px before; 1,995px at rest at 1440x900.

DONE-WHEN NOT FULLY MET - stated per CLAUDE.md rather than marked complete:
"no single view exceeds roughly two screen heights at rest" reads 2.22
screens (1995/900). The remaining gap is page chrome this wave reworks:
.ctx-bar (67px, T7.4) and .release-banner (45px, T7.5). The criterion was
already amended once (D3, "at rest") and is not being moved again to fit;
tests/form_structure_check.py keeps the check red and it is re-measured at
the end of wave 7. Every other done-when entry passes.

Backlog: BL-001's cause corrected a third time - at rest the overflow is
help.js's .help-tip::after tooltip (481 vs 390), the S8 component T9.5
rebuilds; the tables still overflow only when expanded. Deliberately not
fixed here - a fix would be thrown away with the component at T9.5.

Verification (each probe run alone): form_structure_check 50/51 (the height
check above), sections_check 95/95, generalinfo_check 49/49, frame_check
39/39 regression pass.

Items: F6, D3, BL-013, BL-001 (re-measured)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/waves/backlog.md

@@ -110,6 +110,19 @@ deliberately deferred.
   creator at 1440px. Capture now reports overflow on 1 of 14 shots instead of 5. What
   remains is the creator at **390px** (485px of content), which is its own layout rather
   than the shared chrome. Left open so `T7.1` still checks it.
+- **Update, T7.2 - the data-table attribution is spent as well, and the cause has
+  moved a third time.** T7.2 collapses every section at rest, and a collapsed card's
+  tables are `hidden` - they lay out nothing. The at-rest overflow is now
+  **scrollWidth 481 vs 390**, and the widest box is `help.js`'s `.help-tip::after`
+  tooltip, which is rendered (not `display:none`) even when idle and escapes its
+  16px badge to the right. The tables still overflow **when their section is
+  expanded** - that half of the T7.1 note stands and still belongs to a layout
+  decision (scroll container, stacked card, or fewer columns).
+  **Deliberately not fixed in T7.2:** the help tip is the `S8` component, rebuilt
+  whole at `T9.5` - a fix here would be thrown away with the component. `T9.5`
+  owns this entry now. `tests/form_structure_check.py` reports the measurement on
+  every run, and `tests/frame_check.py` keeps the failure pinned so the entry
+  cannot be closed by silence.
 
 ### BL-002 — `outline: none` appears three times in the wizard sheet, not once