feat(pftools): enhance function failure handling with retry logic

[freeznet]

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[Copilot]

Pull request overview

This PR enhances the Pulsar Function Manager's error handling by adding retry logic and failure categorization. It introduces a failure cache to track function conversion failures, classifies them as permanent, retryable, or unknown, and implements smart retry behavior to avoid excessive logging and retry attempts for permanent failures.

Changes:

• Added failure state tracking with configurable retry intervals based on failure classification
• Introduced error categorization to distinguish between permanent failures (e.g., no input topics, schema conversion errors) and retryable failures (e.g., network errors, auth errors)
• Enhanced schema fetch error handling to preserve error information for better classification

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pkg/mcp/pftools/types.go	Adds failedFunctions map to track failure states, SchemaFetchError field to preserve schema fetch errors, and defines failure categories and state structure
pkg/mcp/pftools/manager_failure_cache_test.go	Provides unit tests for failure skip and logging decision logic
pkg/mcp/pftools/manager.go	Implements failure caching logic in updateFunctions(), adds helper functions for hash computation and failure decision-making, and enhances error handling in function conversion
pkg/mcp/pftools/errors.go	Introduces new sentinel errors and classifyConvertError() function to categorize failures
pkg/mcp/pftools/errors_test.go	Adds test coverage for error classification logic

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