Notes how ADR-0005's hover row and clause 7f read against the layer

[johnnyt]

What

ADR-0005's Note of 2026-09-28, which flips the three Amendments of that date, answers clause 7f's "draws what the server computed" with a row whose last clause says the Map hook's hover "swaps and restores the description region's text from the store the server rendered". Since ADR-0018's Note of 2026-09-29 ("selection speaks, hover is silent") the hook draws a hover in a separate hover layer and never writes the region; the Note of 2026-09-29 on ADR-0005 that lists the hook's hover handlers reads them against "holds no behaviour" only.

This PR appends one dated foot Note to docs/adr/0005-liveview-editor.md saying how that row, clause 7g's hover sentence and clause 7f's second permitted write ("a swap of one server-rendered text for another in a region the server rendered, put back when the pointer leaves") read against the layer. The Note carries no Status line, decides nothing, and edits no line above it: git diff origin/main -- docs/adr/ shows 78 added lines and zero removed. No changelog fragment: changelog.d/README.md excludes docs and ADRs.

Refs: sb-4f9n

Gate

Full mix quality green on the committed tree (3,951 of 3,951 tests, 95.3% coverage, dialyzer clean, ADR cites green: every record citation resolves and is unmoved).

Review (in-turn, direction check of the record text)

Every claim was checked against the repo at 4fdf7f8 (main when this branch was cut), and every code cite is anchor first, line second. def description_region (map_regions.ex:227) renders the layer with the region's id plus -hover, aria-hidden="true", hidden and phx-update="ignore" (:259) inside sb-map__description-frame. export function hover (statifier_blocks_map.js:740) shows by copying the store entry's markup into the layer, setting data-map-hover and unhiding it (:755-757), and restores by hiding, emptying and dropping the mark (:744-746); no line of it looks the region up. The CSS rule headed .sb-map__description-hover:not([hidden]) + .sb-map__description (statifier_blocks.css:5036) sets the region's opacity: 0 while the layer shows. The tests named in the Note exist at the cited lines: map_hover_test.exs:62 and :149, map_regions_test.exs:404. The record cites :13684, :13706 and :14107 are the flip Note's heading, the row and the later Note's heading at 4fdf7f8. The Note reads the clause, it does not change it: the clause's three permitted writes stand, and the hover write is read as the second, done in an element the server keeps out of patching. It is appended at the end of the file, so no line another record cites moves. Considered and rejected: treating the data-map-hover attribute as a fourth kind of write (it is written on the same server-rendered element as the swap and dropped by the same restore, so it is read as part of the swap, as the earlier Note of 2026-09-29 already describes it).