docs(stammbaum): ADR-030 tidy-tree layout, supersede ADR-026 packer, refresh glossary (#724)

Review follow-up (Markus/Architect): ADR-026 pre-committed a successor ADR if the
in-house layout stopped converging; its UX stop-trigger (Albert smeared across the
canvas) fired. ADR-030 records the bottom-up tidy-tree, the module split, and the two
maintainer-confirmed decisions (hybrid intra-family, per-bloodline width metric),
superseding ADR-026's block-packer in part (no-dagre + seeded-rank retained). GLOSSARY
replaces the deleted sibling-block / parented / anchor-index vocabulary with the new
family-forest model (unit, tidy tree, structural owner, bloodline, cross-link).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/adr/026-stammbaum-layout-in-house.md

@@ -1,10 +1,14 @@
 # ADR-026 — In-House Stammbaum Layout, dagre Evaluated and Deferred
 
 **Date:** 2026-05-28
-**Status:** Accepted
+**Status:** Accepted — superseded in part by [ADR-030](./030-stammbaum-bloodline-tidy-tree-layout.md)
 **Issue:** #361
 **Supersedes:** _none_
-**Supersedes-on-trigger:** A future ADR-027 if any acceptance criterion below stops converging in-house.
+**Superseded-by:** ADR-030 (#724) replaces the **per-generation block packer** below with
+a bottom-up tidy-tree after its position-within-rank model stranded ancestors and smeared
+bloodlines across the canvas — the UX stop-trigger named in this ADR. The **in-house /
+no-dagre** decision and the seeded-rank invariant (#689) are retained.
+**Supersedes-on-trigger:** _(triggered)_ The UX stop-trigger fired; see ADR-030.
 
 ---
 
@@ -117,6 +121,7 @@ threshold, so `packBlocks.ts` is **not** yet warranted.
   is the source-of-truth probe against live data; the function is the
   capture-time and fixture-time signal that the predicate's count crossed
   zero.
+
 - **AC6 — Bundle-impact gate (≤ 40 kB gzipped on `/stammbaum`).** Moot under
   this ADR; reactivates only under ADR-027 (dagre adoption).
 - **AC7 — Visual regression at 320 / 768 / 1440.** `toHaveScreenshot()`

docs/adr/030-stammbaum-bloodline-tidy-tree-layout.md

@@ -0,0 +1,110 @@
+# ADR-030 — Stammbaum Bloodline-Contiguous Tidy-Tree Layout
+
+**Date:** 2026-06-04
+**Status:** Accepted
+**Issue:** #724
+**Supersedes:** ADR-026 (in part — the per-generation block-packer decision and its
+position-within-rank fix path; the in-house / no-dagre decision and the seeded-rank
+invariant from #689 are retained)
+
+---
+
+## Context
+
+ADR-026 kept Stammbaum horizontal placement in-house with a **per-generation block
+packer** and pre-committed a successor ADR "if any acceptance criterion stops
+converging in-house." Its single UX stop-trigger was Albert de Gruyter's marriages
+failing the read test.
+
+The block packer hit a worse, structural failure: it placed each generation
+**independently**, centring sibling blocks under already-placed parents and only ever
+**shoving right** on collision. Two consequences followed — a deep branch that could
+not fit at its ideal centre dragged everything downstream rightward and stranded the
+ancestor at the **left edge** of its own descendants; and a parent placed before its
+descendants existed could never be re-centred over them. Extreme symptom: Albert de
+Gruyter (G0) far left, a great-great-grandchild far right — one bloodline smeared
+across the full canvas. That is exactly the "UX failure against the canonical fixture"
+ADR-026 named as the trigger to revisit the layout.
+
+## Decision
+
+**Replace the per-generation block packer with a bottom-up "tidy tree"
+(Reingold–Tilford / Walker contour pack), still in-house, no new dependency.**
+
+The horizontal `x` rewrite is split into three reviewable, unit-tested modules
+(mirroring the `panZoom.ts` / `panZoomGestures.ts` / `animateView.ts` split):
+
+- **`layout/tidyTree.ts`** — domain-agnostic contour packer over abstract
+  `{ id, width, children, level? }` nodes, zero generated-API imports. Contours are
+  indexed by **absolute generation level**, not tree depth, so unrelated roots at
+  different generations share x-columns instead of smearing the forest wide.
+- **`layout/familyForest.ts`** — all genealogy semantics: the **unit** model (a
+  bloodline-carrying primary plus the spouse(s) absorbed into its run),
+  `pickStructuralOwner` (lower birthYear, then stable id), loose-spouse absorption,
+  multi-spouse runs (#361), sibling/branch order (birthYear ASC NULLS LAST →
+  displayName → id), intra-family resolution, and cross-link classification.
+- **`layout/buildLayout.ts`** — orchestrates forest → tidy-pack → per-person
+  positions. `assignRanks` (y from rank, #689 seeding), the `generations` map, and
+  `computeViewBox` are reused **unchanged**; `x` comes from structure, `y` from rank.
+
+Two decisions taken during implementation and confirmed with the maintainer:
+
+1. **Intra-family marriage = hybrid.** A couple is always exactly adjacent in the
+   owner's run. When the two spouses' parents sit at the **same structural level** the
+   displaced parent edge renders as a normal solid connector (the "adjacency" case);
+   when they are **cross-level** (e.g. the canonical Clara⚭Herbert, where one parent
+   is nested under Albert and the other hangs off a separate root), the structural
+   owner keeps the hierarchy edge and the other parent→spouse edge renders as a
+   distinct cross-link.
+2. **Cross-link is rendered with a distinct `2 6` dash at 0.7 opacity** in
+   `StammbaumConnectors.svelte` — never the `4 4` ended-marriage cadence. Geometry
+   still lands on the correct child top, so meaning is carried redundantly (WCAG
+   1.4.1); the 0.7 opacity clears the WCAG 1.4.11 3:1 non-text floor.
+
+## Consequences
+
+### Accepted
+
+- **Ancestor centring** — every unit is centred over its child-units' span (named-bug
+  guard `great_great_grandparent_is_not_stranded_left_of_descendants` + a fixture-wide
+  loop over canonical and synthetic trees).
+- **Bloodline contiguity** — each bloodline is one band with no foreign node
+  interleaved. Albert de Gruyter's bloodline shrank from a full ~4860px smear to
+  ~960px.
+- **#361 / #689 preserved** — multi-spouse runs in marriage-year order, seeded ranks,
+  spouse pull-down; the existing `buildLayout.test.ts` cases stay green.
+- **Determinism** — every comparator ends in a stable id; a seeded permutation of
+  nodes/edges yields byte-identical positions.
+- **Fail-closed on cycles** — `assignRanks`' iteration ceiling plus a forest structure
+  (each unit has ≤1 hierarchy parent, cycles are unreachable from roots) guarantee a
+  finite layout with every node placed exactly once.
+
+### Trade-off — total canvas width replaces the ADR-026 width assumption
+
+Centring every ancestor inherently makes a forest of ~24 root-bands **wider** overall
+than the old per-generation left-packer that interleaved everyone into compact shared
+rows (canonical: ~7960px vs the old ~4860px). Total canvas width is therefore the
+wrong success metric; **per-bloodline span** is. The width regression test asserts
+each contiguous bloodline stays far under the old full-canvas smear. The wider canvas
+is navigated by the pan/zoom from #692 (ADR-027) and is an accepted trade-off for
+readability.
+
+### Operational
+
+- **No CI, image, compose, or dependency change.** Pure frontend layout. The
+  `d3-flextree` escape hatch from #724 was not needed.
+
+### Deferred (follow-ups, per #724)
+
+- Connector legibility at 320px — the issue's "open verification"; a manual
+  `/stammbaum` pass, with a connector-clarity issue spun only if drops/cross-links
+  tangle.
+- Polished cross-link routing + a relationship tooltip.
+
+## Notes
+
+- ADR-026's retained parts: the **no-dagre / in-house** decision and the seeded-rank
+  invariant (#689) still hold — this ADR changes only _position-within / across_ rank,
+  not rank assignment, and adds no dependency.
+- The `validateFixture` sanity gates and the AC3 revisit probe from ADR-026 are
+  unchanged.