Closes #25882

Problem

Typing indicators can expire during long LLM inference. Some channels (for example Matrix) rely on a server-side typing TTL, so a single typing event at reply start disappears before the model finishes.

Root Cause

createTypingCallbacks only sent typing on reply start and did not refresh it while inference was still running. Once the platform TTL elapsed, the indicator dropped even though processing continued.

Fix

• Add a keepalive loop in createTypingCallbacks (default 3s) that re-sends typing until cleanup
• Unify onIdle / onCleanup cleanup to stop the keepalive timer and optionally send stop
• Deduplicate stop calls across idle + cleanup and avoid overlapping keepalive start() calls
• Keep the change in the shared channel typing helper so channel integrations inherit the fix without per-plugin changes

Testing

• pnpm exec vitest run --config vitest.unit.config.ts src/channels/channel-helpers.test.ts --maxWorkers=1 ✅
• Added fake-timer coverage for keepalive refresh and cleanup timer clearing
• pnpm test:fast -- src/channels/channel-helpers.test.ts was also attempted, but this script runs the full unit suite in this repo and hit unrelated existing failures (e.g. src/telegram/bot.media.downloads-media-file-path-no-file-download.test.ts, src/plugins/discovery.test.ts)

Greptile Summary

Adds a keepalive mechanism to typing indicators so they remain visible during long LLM inference operations. Previously, typing indicators expired when platform TTLs elapsed, especially on channels like Matrix. The fix introduces a 3-second refresh loop that re-sends typing events until cleanup, along with deduplication logic to prevent multiple stop calls.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The implementation is clean, well-tested, and solves a real UX issue. The keepalive logic correctly prevents overlapping calls with the keepaliveStartInFlight flag, properly clears timers on cleanup, and deduplicates stop calls with the stopSent flag. Test coverage is comprehensive, including fake timer tests for the keepalive mechanism and deduplication edge cases.
• No files require special attention

_{Last reviewed commit: 03db125}