fix: remove 500-row cap that truncated viewer count displays

[chiefmojo]

Problem

clampLimit() in _helpers.ts hard-caps query limits at 500 rows. The viewer's trace and episode count displays fetch the first N rows to count totals, so any store with more than 500 items shows a truncated count.

Fix

Raise the cap from 500 to 100,000. This is a safety guard against pathological inputs, not a query-size policy — reasonable operators setting limit: 10_000 for bulk exports should not be silently truncated.

export function clampLimit(n: number): number {
  if (!Number.isFinite(n) || n <= 0) return 50;
  return Math.min(Math.trunc(n), 100_000);
}

[Memtensor-AI]

Automated Test Results: FAILED

Cloud test-engine rerun against dev-v2.0.22 failed.

• Run: tr-e1b6e067-ca4 on cloud test-engine 10011

• Verdict: fail_code_bug

• Summary: Tests failed. Failed cases: test -- tests/unit/pipeline/memory-core.test.ts tests/unit/server/http.test.ts

• memos_local_plugin/unit: 102 passed, 1 failed, 0 skipped

Failed cases:

• test -- tests/unit/pipeline/memory-core.test.ts tests/unit/server/http.test.ts: ry shape the viewer expects
  AssertionError: expected 500 to be 200 // Object.is equality

• Expected

• Received

• 200

• 500

❯ tests/unit/server/http.test.ts:834:22
832| it("GET /api/v1/overview returns the summary shape the viewer expect…
833| const r = await fetch(${handle.url}/api/v1/overview);
834| expect(r.status).toBe(200);
| ^
835| const body = (await r.json()) as {
836| ok?: boolean;

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Do not merge until this is fixed and cloud tests pass.