Add a bisect hook (?limit=) to the internal snapshot trigger

The cap raise 25 -> 500 made an induced snapshot 502 at 13.4s and the run
did not complete in background either, while a 25-prop run had completed
in 16.3s. That rules out a simple duration timeout and means the cause has
to be measured, not guessed. ?limit= bounds one run so the regression can
be bisected without a prod env change; omitted, the real DEFAULT_LIMIT
applies.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QJs13VsyiSKYQP6rj3NNmc

src/services/snapshotService.js

@@ -400,6 +400,11 @@ async function runSnapshot(sport, opts = {}) {
   // letting it write (we re-write an ENRICHED version below).
   let envelope = null;
   await deps.gradeAndCacheSlate(sp, props, {
+    // Bisect hook (2026-08-01): lets the internal trigger run a bounded slate
+    // without a prod env change, so a cap regression can be isolated by
+    // measurement instead of guessed at. Omitted => gradeSlateService's own
+    // DEFAULT_LIMIT (the real production value).
+    ...(Number(opts.limit) > 0 ? { limit: Number(opts.limit) } : {}),
     source: (odds && odds.provider) || 'odds-api',
     now: deps.now,
     cacheSet: async (_k, v) => { envelope = v; },