docs: amend constitution to v1.1.0 (Observability for tracing migration)

Principle V now reflects the merged tracing migration (#148):
- tracing + tracing-opentelemetry spans in every build, with OTLP export
  gated on OTLP_OTLS_ENDPOINT;
- no manual Context threading;
- every spawn / fan-out carries its parent span;
- RUST_LOG gates span export (run at info/debug).
Layer and Tech Stack wording matches.

Also corrects stale "release builds only" telemetry notes in CLAUDE.md and
.env.example, updates the CLAUDE.md dependency list, and fixes the README's
RUST_LOG default. It also documents OTLP_OTLS_ENDPOINT in the README, as
Principle IV requires.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.env.example

@@ -28,7 +28,9 @@ HLS_CONCURRENCY=2
 HLS_TIMEOUT_SECONDS=900
 PLAYLIST_CLEANUP_INTERVAL_SECONDS=86400
 
-# ── Telemetry (release builds only) ─────────────────────────────────────
+# ── Telemetry ────────────────────────────────────────────────────────────
+# Span export over OTLP in any build when set (unset = spans stay local).
+# RUST_LOG also gates span export: keep it at info or debug.
 # OTLP_OTLS_ENDPOINT=http://localhost:4317
 
 # ── AI Insights — Ollama (local LLM) ────────────────────────────────────