fix: resolve recorder upload task conflicts

[shark0F0497]

Pull Request Checklist

Please ensure your PR meets the following requirements:

• Code follows the style guidelines
• Tests pass locally
• Code is formatted
• Documentation updated if needed
• Commit messages follow conventional commits
• PR description is complete and clear

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Summary

This PR prevents recorder config/begin flows and finish callbacks from racing with tasks that have already moved into upload-related states. It also expands transfer status handling so Keystone can reconcile missed upload requests from transfer status snapshots.

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Motivation

• Avoid starting or configuring a task after the same task has already moved into uploading, completed, or another non-runnable status.
• Make recorder finish callbacks idempotent for upload states and reject terminal states instead of sending duplicate upload requests.
• Recover from transient transfer disconnect/write failures by re-queueing eligible upload_request messages when transfer status proves the upload is not already active.

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Changes

Modified Files

• [internal/api/handlers/axon_rpc.go](internal/api/handlers/axon_rpc.go) - Adds task status guards before recorder config and begin RPC calls, including recorder state sync/freshness checks for begin.
• [internal/api/handlers/task.go](internal/api/handlers/task.go) - Rejects config reads for non-pending tasks and tightens finish callback handling across uploadable, idempotent, and terminal statuses.
• [internal/api/handlers/task_uploading.go](internal/api/handlers/task_uploading.go) - Aligns upload status transition behavior with the guarded finish callback flow.
• [internal/api/handlers/transfer.go](internal/api/handlers/transfer.go) - Parses richer transfer status payloads and reconciles eligible failed upload requests with a cooldown.
• [internal/services/transfer_hub.go](internal/services/transfer_hub.go) - Adds transfer status fields and upload snapshot records used by the status endpoint and reconciliation.
• [internal/api/handlers/recorder_axon_interaction_test.go](internal/api/handlers/recorder_axon_interaction_test.go) - Updates recorder RPC tests for the new pre-RPC task guards.
• [internal/api/handlers/task_state_recovery_test.go](internal/api/handlers/task_state_recovery_test.go) - Adds finish callback idempotency, terminal status, and config guard coverage.

Added Files

• [docs/designs/task-recorder-upload-guard-design.md](docs/designs/task-recorder-upload-guard-design.md) - Documents the recorder/upload guard design.
• [internal/api/handlers/transfer_status_test.go](internal/api/handlers/transfer_status_test.go) - Covers transfer upload snapshots and upload request reconciliation behavior.

Deleted Files

• None

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Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update (documentation changes only)
• Refactoring (code improvement without functional changes)
• Performance improvement (code changes that improve performance)
• Test changes (adding, modifying, or removing tests)

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Impact Analysis

Breaking Changes

None

Backward Compatibility

Fully backward compatible. Existing recorder and transfer APIs remain the same; invalid task-state transitions now return conflict responses instead of forwarding unsafe RPC/upload requests.

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Testing

Test Environment

• Local CLI environment
• Go test command executed outside the sandbox because these tests use httptest listeners.

Test Cases

• Unit tests pass locally: go test -run 'TestRecorder|TestRecordingFinish|TestGetTaskConfig|TestTransferStatus' ./internal/api/handlers/...
• Integration tests pass locally
• E2E tests pass (if applicable)
• Manual testing completed

Manual Testing Steps

Not run.

Test Coverage

• New tests added
• Existing tests updated
• Coverage maintained or improved

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Screenshots / Recordings

Not applicable.

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Performance Impact

• Memory usage: No change
• CPU usage: No change
• Throughput: No change
• Lock contention: No change

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Documentation

• README.md updated
• ARCHITECTURE.md updated
• CONTRIBUTING.md updated
• API documentation updated
• Design docs updated in docs/designs/
• No documentation changes needed

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Related Issues

• N/A

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Additional Notes

• Full integration tests were not run locally.

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Reviewers

None requested.

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Notes for Reviewers

• Please focus on task status transitions in recorder config/begin and finish callback handling.
• Please verify transfer status reconciliation only re-queues upload requests for recoverable send failures and skips already active uploads.

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Checklist for Reviewers

• Code changes are correct and well-implemented
• Tests are adequate and pass
• Documentation is updated and accurate
• No unintended side effects
• Performance impact is acceptable
• Backward compatibility maintained (if applicable)