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>

CLAUDE.md

@@ -684,7 +684,7 @@ Optional:
 WATCH_QUICK_INTERVAL_SECONDS=60        # Quick scan interval
 WATCH_FULL_INTERVAL_SECONDS=3600       # Full scan interval
 DATE_BACKFILL_MAX_PER_TICK=500         # Cap on canonical-date drain per watcher tick
-OTLP_OTLS_ENDPOINT=http://...          # OpenTelemetry collector (release builds)
+OTLP_OTLS_ENDPOINT=http://...          # OTLP collector for span export (any build; unset = no export)
 
 # AI Insights Configuration
 OLLAMA_PRIMARY_URL=http://desktop:11434        # Primary Ollama server (e.g., desktop)
@@ -944,7 +944,7 @@ side if exposing beyond a trusted network.
 - **image**: Thumbnail generation
 - **walkdir**: Directory traversal
 - **rayon**: Parallel processing
-- **opentelemetry**: Distributed tracing
+- **tracing** + **tracing-opentelemetry** + **tracing-actix-web**: spans (exported via `opentelemetry-otlp`)
 - **bcrypt**: Password hashing
 - **infer**: Magic number file type detection