docs(issue-29): record phase 2 observation schedule

Refs: #29

Author: josecelano

docs/issues/ISSUE-29-research-high-cpu-load-after-udp-fix.md

@@ -97,7 +97,8 @@ step.
 
 - [x] Remove `"443:443/udp"` from the Caddy service in `server/opt/torrust/docker-compose.yml`.
 - [x] Apply only that change on the live server and restart only Caddy.
-- [ ] Observe CPU, request rates, and external service health for an agreed window.
+- [ ] Observe CPU, request rates, and external service health at T+1 h (≈ 2026-05-04 16:31 UTC)
+      and again the following day (2026-05-05).
 - [ ] Decide whether Caddy CPU dropped materially enough to keep HTTP/3 disabled.
 
 Execution and immediate post-change checks are recorded in

docs/issues/evidence/ISSUE-29/01-phase2-disable-http3-execution.md

@@ -106,8 +106,17 @@ From `https://newtrackon.com/raw` during this window:
 - `https://http1.torrust-tracker-demo.com:443/announce` -> `Working`
 - `udp://udp1.torrust-tracker-demo.com:6969/announce` -> `Working`
 
-## Next Step
+## Observation Schedule
 
-Phase 2 observation remains open. Keep this single change in place and collect
-an agreed observation window before deciding whether to keep HTTP/3 disabled
-permanently or revert.
+Agreed observation windows for Phase 2:
+
+| Checkpoint | Target time (UTC)        | Status  |
+| ---------- | ------------------------ | ------- |
+| T+1 h      | 2026-05-04 16:31         | pending |
+| T+next day | 2026-05-05 (any morning) | pending |
+
+Capture the same metrics at each checkpoint: `mpstat`, `docker stats`, Prometheus
+HTTP1/UDP1 rates, and a `newtrackon.com/raw` sample.
+
+Keep this single change in place until both checkpoints are completed before
+deciding whether to keep HTTP/3 disabled permanently or revert.