fix(spec): re-derive the conversion-fixture count after merging origin/main

The origin/main merge (79d709d) brought in a new conversion registered at
protocol 18 (dashboard-widget-chart-config-structure-removed, #19363),
moving ALL_CONVERSIONS from 97 to 98 at this head. Re-counted at runtime
post-merge; the below-floor count (10) is unaffected since the new entry is
above the floor.

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

Author: claude

.changeset/19056-migration-support-floor-16.md

@@ -59,7 +59,7 @@ Counted on `src/migrations/registry.ts` at `e6a03e649` (17,718 lines):
 Everything but the first row stays. What the raise buys is a **narrower support
 promise**: six permanently-replayable chains no longer have to be maintained,
 and the CI replay shrinks to the range the project actually promises — 10 of the
-97 conversion fixtures leave the chain-replay gate, because the chain no longer
+98 conversion fixtures leave the chain-replay gate, because the chain no longer
 reaches the major that graduated them.
 
 ## What was deliberately NOT removed