Never mix the share error with the list error: the retry button must belong to the list read #987

Symptom

In Sharing → Share with a friend, a failed Share click and a failed list read share one note slot, and the retry link is drawn for any error — so after a failed share the card offers Try again, which does not retry the share: it re-reads the list and, on success, wipes the share's error message.

Where, at main 99cbb1a1 (plugins/social/client.js)

• One slot: note state :3152; a failed list read writes { tone: 'error' } at :3169; a failed share click writes { tone: 'error' } at :3200; a successful share writes { tone: 'ok' } at :3195.
• The button is keyed on the tone only: :3226-3228 renders Try again whenever note.tone === 'error', and onClick calls load() — the list reader.
• load() clears any error note when it succeeds: :3164 setNote(previous => (previous?.tone === 'error' ? null : previous)). So pressing it after a failed share erases the share's own error and does not retry the share.
• The same coupling reaches the empty state: note?.tone !== 'error' at :3209 suppresses "No friends left to share with" for a share error too, which the list had nothing to do with.

Reviewer's non-blocking on #985 says the same thing; both halves of it (this button, and that gate) are one root cause: the note has no source.

Expected

• Try again belongs to a failed list read only. A failed share keeps its message, and the button either does not appear or reads Reload the list and is visibly about the list.
• A successful list read clears only a list error; it never clears a share's error.
• "No friends left to share with" is suppressed by a list error only.

Acceptance

1. Red test first: the fake host rejects social/share-with-friend while social/share-friends works — after the click the card must not offer a retry that re-reads the list (or must offer one labelled Reload the list), and a later successful read must not clear the share error. Red on main, green after the fix.
2. A failed list read still offers a retry, clicking it re-reads, and a successful read clears that error.
3. The empty-state gate is driven by a list-sourced error only; add the case that keeps it honest (Reviewer's Keep the share list when a read fails or races a revoke (#984) #985 non-blocking: the current note?.tone !== 'error' gate has no test, and the knife is green).
4. Row keys, the 5s poll (:3177), the [bot?.id] reset (:3172-3180) and the read epoch/seq from The sharing panel claims "No friends left to share with" when a friend list read is stale or fails #984 (:3156-3167) are untouched.
5. plugins/social suite green; changelog.d/ fragment; docs/subsystems/social.md if the wording changes.

Out of scope

• The sharing panel claims "No friends left to share with" when a friend list read is stale or fails #984's list-keeping behaviour (merged, 99cbb1a1); this is only about which failure a button speaks for.