Validate BOLT-2121 Linear identifier and decide next step

PR #15705 for the Leap timeout override closed unmerged (2026-09-24 12:10 UTC). Linear identifier BOLT-2121 could not be resolved via API. Verify the correct Linear issue identifier, then ask Slava whether to reopen #15705, open a fresh PR from cato/bolt-2121-leap-generation-timeout-override, or deprioritize the timeout work.