docs: pages for chaos testing and resilience evaluators

[ybdarrenwang]

Description

Adds documentation pages for the chaos testing module and three new resilience evaluators in Strands Evals:

• Chaos Testing page (chaos_testing.mdx): Overview and guide for the chaos testing framework, covering ChaosPlugin, ChaosCase, ChaosExperiment, chaos effects (pre-hook and post-hook), ChaosCase.expand() for Cartesian product generation, and integration with ToolSimulator
• FailureCommunicationEvaluator page: Documents the evaluator that assesses how well an agent communicates tool failures to users, using a five-level scoring rubric (No Communication → Excellent Communication)
• PartialCompletionEvaluator page: Documents the evaluator that scores what fraction of a user's goal was achieved despite failures, returning a continuous 0.0–1.0 score
• RecoveryStrategyEvaluator page: Documents the evaluator that scores the quality of an agent's recovery actions (retries, fallbacks, tool switching) when tools fail

Also updates:

• Evaluators index: Adds a new "Resilience Evaluators" subsection to the evaluators index page
• navigation.yml: Wires the new pages into the evals-sdk sidebar

Related Issues

strands-agents/evals#114
#2697

Type of Change

Documentation update

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran npm run dev

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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