feat: initialize observability instrumentation implementation

- Create PROGRESS.md with 29 tasks across 6 phases
- Update README.md with started timestamp
- Spec approved and ready for implementation

Implements: SPEC-2025-12-25-001

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: zircote

docs/spec/active/2025-12-25-observability-instrumentation/ARCHITECTURE.md

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+# Changelog
+
+All notable changes to this specification will be documented in this file.
+
+## [Approved] - 2025-12-26T00:31:42Z
+
+### Approved
+- Spec approved by Robert Allen <zircote@gmail.com>
+- Status changed: in-review → approved
+- Ready for implementation via /claude-spec:implement observability-instrumentation
+
+## [1.1.0] - 2025-12-26
+
+### Added
+- Phase 6: Local Observability Stack & Documentation (4 tasks)
+  - Docker Compose stack with OTEL Collector, Prometheus, Grafana, Tempo, Loki
+  - Pre-built Grafana dashboards for memory operations and hook performance
+  - Provider documentation for 7 observability platforms
+  - Project documentation updates
+
+- Task 1.5: SessionIdentifier for multi-tenant telemetry distinguishability
+  - SessionInfo frozen dataclass
+  - Privacy-preserving hashes (repo path, username)
+  - Format: `{hostname}:{repo_hash}:{timestamp}:{uuid_suffix}`
+
+- Multi-Session Distinguishability requirements (REQUIREMENTS.md)
+  - FR-007: Session identification in all telemetry (P0)
+  - FR-205-208: Docker Compose, dashboards, provider docs (P2)
+  - Session ID strategy and resource attributes
+
+- ADR-010: Session Identification Strategy
+- ADR-011: Local Observability Stack (Docker Compose)
+
+- Complete Docker Compose stack architecture (ARCHITECTURE.md)
+  - Component 7: SessionIdentifier
+  - Stack architecture with OTEL Collector configuration
+  - Grafana datasources and dashboard provisioning
+  - File structure for docker/ directory
+
+### Changed
+- Implementation plan now has 6 phases, 29 tasks (was 5 phases, 24 tasks)
+- Estimated effort updated to 7-10 days (was 5-7 days)
+- measure_duration decorator now includes session_id label
+
+## [1.0.0] - 2025-12-25
+
+### Added
+- Complete requirements specification (REQUIREMENTS.md)
+  - 6 P0 functional requirements
+  - 6 P1 functional requirements
+  - 4 P2 functional requirements
+  - Non-functional requirements for performance, compatibility, reliability
+
+- Technical architecture design (ARCHITECTURE.md)
+  - 6 core components: MetricsCollector, SpanContext, StructuredLogger, measure_duration, ObservabilityConfig, ExportBackends
+  - Module structure under `src/git_notes_memory/observability/`
+  - Integration points for all services and hooks
+  - Security and performance considerations
+
+- Implementation plan with 5 phases, 24 tasks (IMPLEMENTATION_PLAN.md)
+  - Phase 1: Core Infrastructure
+  - Phase 2: Instrumentation
+  - Phase 3: Structured Logging
+  - Phase 4: CLI & Export
+  - Phase 5: OpenTelemetry Integration
+
+- 9 Architecture Decision Records (DECISIONS.md)
+  - ADR-001: Optional dependencies via extras
+  - ADR-002: Unified debug levels
+  - ADR-003: JSON structured logging as default
+  - ADR-004: In-memory metrics with rolling window
+  - ADR-005: Contextvars for span propagation
+  - ADR-006: Decorator pattern for timing
+  - ADR-007: Prometheus histogram bucket configuration
+  - ADR-008: Graceful degradation pattern
+  - ADR-009: Command naming convention
+
+- Codebase analysis and research findings (RESEARCH_NOTES.md)
+  - Current logging inventory (92 statements)
+  - Critical operation paths mapped
+  - 5 silent failure points identified
+  - Hook timeout configuration documented
+  - External research on OpenTelemetry, Prometheus, structlog
+
+### Research Conducted
+- OpenTelemetry Python best practices for optional dependencies
+- Prometheus histogram bucket recommendations aligned with SLOs
+- structlog vs python-json-logger comparison
+- Codebase analysis via parallel exploration agents
+
+## [Unreleased]
+
+### Added
+- Initial project creation
+- Requirements elicitation begun
+- Imported requirements from GitHub Issue #10