feat(observability): enable full Workers Logs traces (100% sampling)

cloudflare-worker/CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- Enable Workers Logs with `head_sampling_rate = 1` and `invocation_logs = true` — every cron tick produces a full trace, browsable in the CF dashboard for 3 days.
+
 ## [0.1.0] - 2026-05-09
 
 ### Added

cloudflare-worker/README.md

@@ -135,7 +135,7 @@ The request pins `anthropic-beta: experimental-cc-routine-2026-04-01` (constant
 
 - **Time accuracy**: cron precision on CF Workers is within ~15 seconds — adequate for routine triggering.
 - **No retry**: each `/fire` POST creates a new Claude Code session — retrying multiplies sessions and burns quota. The worker logs failures and moves on.
-- **Logs**: `wrangler tail` streams live; CF dashboard's "Logs" tab persists them per the observability tier.
+- **Logs / traces**: `[observability]` is enabled in `wrangler.toml` with `head_sampling_rate = 1` and `invocation_logs = true` — every invocation produces a structured log + trace, retained per the [Workers Logs retention policy](https://developers.cloudflare.com/workers/observability/logs/workers-logs/) (3 days on the free plan). View live with `npx wrangler tail`, or browse history in the CF dashboard under **Workers & Pages → your worker → Logs**.
 - **Cost**: scheduled handlers count against the Workers Free plan's 100k requests/day budget. 5 daily fires × 30 days = 150 requests/month — negligible.
 
 ## Security

cloudflare-worker/wrangler.toml

@@ -19,6 +19,14 @@ crons = [
   "0 0-17,22-23 * * *", # UTC+7: 00:00 + 05:00..23:00 hourly
 ]
 
-# Built-in observability (free tier supports basic logs).
+# Workers Logs / traces. `head_sampling_rate = 1` keeps 100% of invocations
+# (low volume here — ~20/day — so full retention is free). Drop to e.g. 0.1
+# if traffic ever grows enough to matter.
 [observability]
 enabled = true
+head_sampling_rate = 1
+
+[observability.logs]
+enabled = true
+head_sampling_rate = 1
+invocation_logs = true