Make recipe repairs conditional and keep pasted links out of logs

F1: A candidate or link repair now writes the dinner only if it is still
unarchived and as observed before grounding (normalized_name,
grounding_status, grounding_revision and recipe_id). A dinner renamed or
grounded some other way meanwhile is ErrGroundConflict (409
ground_conflict); one archived, before or during the repair, is
ErrArchived (409 dinner_archived). Manual repairs reject archived dinners
too.

F2: Any failure grounding a candidate or link by hand wraps
ErrGroundFailed, which the API logs as reason=ground_failed with the
dinner id only, never the pasted link or dependency error text.
GroundURL no longer formats the link into its error.

Maestro task 8741cedb-1849-4e3f-8d05-f5648c77c7ee.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/recipes/ground.go

@@ -266,7 +266,7 @@ func (g *Grounder) GroundURL(ctx context.Context, rawURL string) (Grounded, erro
 	}
 	gr, reason, err := g.ground(ctx, rawURL, r)
 	if err != nil {
-		return Grounded{}, fmt.Errorf("recipes: ground %s: %w", rawURL, err)
+		return Grounded{}, fmt.Errorf("recipes: ground pasted link: %w", err)
 	}
 	if reason != nil {
 		return ungroundable(reason)