#17294: docs(telegram): add poll CLI example and constraints

## Summary - add a telegram-specific `openclaw message poll` example to channel docs - document telegram poll constraints: 2-12 options, 5-600 seconds, and `--poll-public` - keep scope docs-only (no runtime changes) ## Verification - checked flags via `openclaw message poll --help` - validated placement in the existing "Limits, retry, and CLI targets" section <!-- greptile_comment --> <h3>Greptile Summary</h3> Added Telegram-specific CLI poll example and documented poll constraints (2-10 options, 5-600 seconds, `--poll-public` flag). The documentation accurately reflects the implementation with the corrected option limit from the previous review thread. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with no risk - docs-only change that accurately documents existing functionality - Documentation-only PR that accurately reflects implementation details verified in source code (`src/telegram/send.ts:979` for maxOptions:10, lines 1049-1050 for 5-600 duration, `src/cli/program/message/register.poll.ts:21` for --poll-public flag). The previously identified issue with 2-12 options has been corrected to 2-10. - No files require special attention _{Last reviewed commit: c068328} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->