Ignore Jaeger file cache in Discord memory alerts

[patroza]

Summary

• read total, anonymous, and file-backed RSS from proc status
• alert for Jaeger only after anonymous memory stays at or above 2 GiB for five watchdog ticks
• keep the existing 768 MiB total-RSS policy for ordinary processes and preserve sustained CPU alerts
• report anonymous memory, file cache, total RSS, and the applied threshold in Discord
• fall back to total RSS at the same 2 GiB threshold if the kernel omits the RSS breakdown

The deployed Badger backend, 14-day retention, and 4 GiB container ceiling remain unchanged. This child PR targets the canonical Discord overlay PR #80.

Verification

• vp test run apps/discord-bot/src/features/Alerts.test.ts (17 passed)
• node_modules/.bin/tsgo --noEmit -p apps/discord-bot/tsconfig.json
• vp lint on the changed files
• vp fmt --check on the changed files
• git diff --check