fix(cli): state the 100-row server cap in alert/alert-event --limit flag help

[ysyneu]

The alert list and alert-event list endpoints reject limit > 100 with InvalidParameter: Limit must be 100 or less. incident list already documents the cap in its --limit flag help ("Max results (max 100)"); this mirrors the same wording onto the two alert verbs.

Rationale: the cap is mentioned in alert list's long description, but a reader (human or agent) who greps the Flags section of --help never sees it and only discovers the cap by hitting the 400. The flag-level note makes the first call correct.

Verification: make + go test ./internal/... green; built binary shows --limit int Max results (max 100) for both verbs; make gen-cards produces no card diff (flag usage strings are not embedded in the generated fences).

[ysyneu]

Extended to insight incidents --limit as well — its endpoint shares the same page-query validator (lte=100), verified in the backend. Other verbs with unstated caps (oncall, incident similar, audit's max-99) are NOT touched here: their caps differ or weren't verified against the backend, so stamping them would be guesswork — separate follow-up if wanted.