Merge branch 'docs/256-claude-md-split' into fix/258-artifact-blob-cursor

Both branches rewrite CLAUDE.md. Mine appended a note about #258 to the
"the catalog stores ids as bytes" section; theirs cuts the file from
4,046 lines to 376 and deletes those write-ups, on the grounds that each
one already exists as a comment beside the code it describes.

Resolved in theirs. Nothing is lost by it: the refactor already states
both halves of the note as broad engineering rules, and cites #258 —
"Encodings are converted at one boundary … a Go `string` cursor against
a BLOB column made the catalog merge loop forever while merging nothing"
and "A loop that must make progress checks that it did … a merge that
lands fewer rows than it read". The detail stays in `artifactKey`'s doc
comment and in `publishedartifact_test.go`'s, which is where the new
file says this class belongs.

e2e/specs/phone-search.spec.ts

@@ -171,8 +171,8 @@ test.describe('search on a phone', () => {
     // Attached, not visible: `wa-dialog`'s host is `display: contents`,
     // so the element carrying the testid always reports hidden — what
     // is visible is the native `<dialog>` inside it. That awkwardness
-    // is written down in CLAUDE.md and is why the assertion that this
-    // is really up is the role query below.
+    // is why the assertion that this is really up is the role query
+    // below.
     await expect(dialog).toBeAttached();
 
     // Named, which `getByRole` can answer and the a11y snapshot cannot