chore(changelog): Add 9.1.0 Phase 3 structural instrumentation entry

Author: fer

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+## [9.1.0] - 2025-11-14
+
+### Added
+
+- Phase 3 structural instrumentation:
+  - `run_structural_validation` aggregator (grammar U1-U3 + field thresholds Φ_s, |∇φ|, K_φ, ξ_C, optional ΔΦ_s drift).
+  - `compute_structural_health` with risk levels and recommendations.
+  - `TelemetryEmitter` integration example (`examples/structural_health_demo.py`).
+  - Performance guardrails: `PerformanceRegistry`, `perf_guard`, `compare_overhead`.
+  - CLI: `scripts/structural_health_report.py` (on-demand health summaries).
+  - Docs: README Phase 3 section, CONTRIBUTING instrumentation notes, `docs/STRUCTURAL_HEALTH.md`.
+- Glyph-aware grammar error factory (operator glyph → canonical name mapping).
+
+### Tests
+
+- Added unit tests for validation, health, grammar error factory, telemetry emitter, performance guardrails.
+
+### Performance
+
+- Validation instrumentation overhead ~5.8% (moderate workload) below 8% guardrail.
+
+### Internal
+
+- Optional `perf_registry` parameter in `run_structural_validation` (read-only timing).
+
+### Deferred
+
+- U4 bifurcation validation excluded pending dedicated handler reintroduction.
+
+### Integrity
+
+- All changes preserve TNFR canonical invariants (no EPI mutation; phase verification intact; read-only telemetry/validation).
+
+## [9.0.2]
+
+Previous release (see repository history) with foundational operators, unified grammar, metrics, and canonical field tetrad.
+
+---
+**Reality is not made of things—it's made of resonance.**