v1.50.1: the v1.50.0 review (HP-1500-01..03)

- HP-1500-02: the stage budget was the absolute document coordinate, so any
  tall dashboard content before the card was billed as header and the stage
  collapsed to 0px. Measure our own chrome relative to the card plus a
  bounded (<=120px) allowance for what the viewport keeps above us; re-measure
  on window resize, remove the listener in disconnectedCallback.
- HP-1500-03, both layers: contentBounds opens a near-zero axis (< ~an icon)
  up to a 200-unit floor and ignores extra points outside a canvas envelope
  (-25%..125%) for FRAMING purposes only; the server bounds layout coordinates
  to +-4 — any finite float used to pass, and one 1e100 hid the plan from
  every viewer. A thin real room keeps its tight frame; the gate sensor past
  the edge still stretches it.
- HP-1500-01: no automatic double-transform — a correct layout and a stranded
  one are indistinguishable, and guessing wrong corrupts good data. Explicit
  admin command houseplan/geometry/repair: dry_run previews, the backup rides
  the same store write, undo restores, and routine layout writes now preserve
  unrelated store keys instead of eating the backup.

Tests: contentBounds guards (unit), layout coordinate bounds + repair
lifecycle (harness), card-below-content smoke. Inventory: 139 / 49 / 42 / 64.

docs/TESTING.md

@@ -239,6 +239,16 @@ Run the *core flows* (marked ★ below) in each environment at least once per mi
       on the plan after a reload. Same for each tap action and each fill mode
       [auto: backend test_every_display_mode_the_editor_offers_is_accepted and
       neighbours, test_a_marker_showing_its_value_can_be_saved]
+- [ ] Card below other dashboard content (v1.50.1, HP-1500-02): place the card
+      after a tall card in a normal dashboard — the plan still gets most of the
+      viewport instead of a zero-height stage [auto: smoke_zoom_out]
+- [ ] Frame never degenerate (v1.50.1, HP-1500-03): a space with one lone
+      marker opens with canvas around it, not an empty scene; an absurd stored
+      coordinate neither hides the plan nor is accepted by the server
+      [auto: unit contentBounds + backend test_layout_coordinates_are_bounded]
+- [ ] Stranded migration repair (v1.50.1, HP-1500-01): geometry/repair with
+      dry_run previews, applies with a backup, undo restores; wrong space is
+      recoverable [auto: test_geometry_repair_is_explicit_previewable_and_undoable]
 - [ ] Editors see the whole canvas (v1.50.0, HP-1490-03): a hand-drawn space
       with one small room opens content-fit in View; switching to the plan
       editor shows the full square with room to draw a second room far away;