feat: Add comprehensive observability CLI for agent telemetry (#360)

Add CLI commands and notebook interface for querying and visualizing OpenTelemetry traces from AgentCore Runtime agents.

## Features

### CLI Commands
- `agentcore obs list`: List traces with filtering by session, agent, time range, and errors
- `agentcore obs show`: Display detailed trace view with span hierarchy and messages

### Core Components
- **CloudWatch Logs Integration**: Query OTEL spans and runtime logs from CloudWatch
- **Message Parser**: Multi-framework support with scope-based routing for LangChain, LangGraph, Strands, and generic OTEL
- **Trace Processor**: Build span hierarchies, calculate durations, filter errors
- **Trace Visualizer**: Rich console rendering with tree views and color coding
- **Query Builder**: Time range filtering, batch pagination, multi-field queries

### Framework Support
- LangChain: Parse nested JSON with tool calls
- LangGraph: Extract input/output messages from instrumentation
- Strands: Parse standard input/output structures
- Generic OTEL: Extract gen_ai events with fallback patterns

### Testing
- Comprehensive E2E tests with real OTEL fixtures
- 210+ unit tests covering all components
- Integration tests for notebook interface
- Mock CloudWatch clients for isolated testing

### Notebook Interface
- `ObservabilityNotebook`: Jupyter-friendly interface for programmatic trace analysis
- Display traces in tables with IPython.display integration

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

Co-authored-by: Claude <[email protected]>

Author: Vivekbhadauria1

src/bedrock_agentcore_starter_toolkit/__init__.py

@@ -1,5 +1,5 @@
 """BedrockAgentCore Starter Toolkit."""
 
-from .notebook.runtime.bedrock_agentcore import Runtime
+from .notebook import Observability, Runtime
 
-__all__ = ["Runtime"]
+__all__ = ["Runtime", "Observability"]

src/bedrock_agentcore_starter_toolkit/cli/cli.py

@@ -8,6 +8,7 @@
     gateway_app,
 )
 from ..cli.memory.commands import memory_app
+from ..cli.observability.commands import observability_app
 from ..utils.logging_config import setup_toolkit_logging
 from .identity.commands import identity_app
 from .import_agent.commands import import_agent
@@ -43,6 +44,9 @@
 # memory
 app.add_typer(memory_app, name="memory")
 
+# observability
+app.add_typer(observability_app, name="obs")
+
 # import-agent
 app.command("import-agent")(import_agent)
 

src/bedrock_agentcore_starter_toolkit/cli/observability/__init__.py

@@ -0,0 +1 @@
+"""Observability CLI commands."""