Add project documentation and Claude instructions

Roadmap, phase specs, pathology catalog, and CLAUDE.md establishing
Ledgerline as an observability learning project built on a deliberately
imperfect seven-service payments backend.

docs/roadmap/phase-10.md

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+# Phase 10 — Package the delivery
+
+*Part of `docs/roadmap/` — see [`intro.md`](intro.md) for platform/background context and [`summary.md`](summary.md) for how every phase fits together. Prev: [`phase-9.md`](phase-9.md) · Next: [`summary.md`](summary.md)*
+
+**Status:** Not started
+
+**Message:** Depends on every prior phase being done — this is the wrap-up,
+not independent work.
+
+**Time-box:** one evening.
+
+Babak gave you a task; deliver it like an engineer, not like a student.
+
+1. **`README.md`** — architecture diagram, one-command start, what each container is
+   for, and a "here's the demo" script.
+2. **The five-minute demo path**, rehearsed:
+   - Delete every dashboard in the Grafana UI, then `ansible-playbook
+     playbooks/grafana-stack.yml` — the whole platform and every dashboard rebuilt
+     from code, one command.
+   - Submit one transaction from the frontend, then follow it through Grafana: RED
+     dashboard → latency spike → exemplar → trace → span → logs for that span → back
+     to the trace. One request, all three signals, no searching.
+   - `make chaos-nightmare && make load-stress` — watch the SLO burn, the alert fire,
+     and the service map turn red at a specific node.
+   - Show `docs/INVESTIGATION.md` and how you found the pathologies.
+3. **The written answers** Babak asked for, as documents in the repo, not as a
+   conversation: `docs/SLO.md`, `docs/PIPELINE-CHOICES.md`,
+   `docs/INVESTIGATION.md`, plus a short `docs/CONCEPTS.md` covering P95/P99,
+   RTO/RPO/SLA/SLO/error budget in your own words.
+4. **The test suite as part of the story.** Show `make test` green, then show the
+   three generations of the call-counting assertion side by side —
+   `docker logs | grep`, then LogQL, then TraceQL — as concrete evidence of what
+   each signal bought you. Most people demo dashboards; almost nobody can show
+   their observability work paying off inside their own test suite.
+5. **A "what I'd do differently in production" section.** Tail sampling instead of
+   100%; Mimir instead of raw Prometheus for retention; Alloy as a DaemonSet;
+   log volume budgeting; PII redaction in the Collector; multi-tenancy. Naming what
+   you *didn't* do, and why, is the strongest signal of seniority in the whole
+   delivery.
+