fix(agent): store managed process logs under tmp

[Nauyix]

Pull Request Checklist

Please ensure your PR meets the following requirements:

• Code follows the style guidelines
• Tests pass locally (make test or make docker-test)
• Code is formatted (make format)
• Documentation updated if needed
• Commit messages follow conventional commits
• PR description is complete and clear

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Summary

This PR moves the default stdout/stderr capture files for agent-managed processes into /tmp/axon-agent/logs. Explicit stdout_log and stderr_log profile overrides continue to work as before.

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Motivation

• Agent-managed one-shot processes such as robot_startup, recorder, and transfer can produce large stdout/stderr logs.
• Keeping default capture files under the persistent agent state directory causes those logs to accumulate over time.
• The new default keeps transient process output in /tmp while preserving configured log paths for deployments that need persistence.

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Changes

Modified Files

• apps/axon_agent/src/process_manager.cpp - Change the default managed-process log directory from state_dir/logs to /tmp/axon-agent/logs.
• apps/axon_agent/test/test_agent_service.cpp - Add coverage for the default transfer stdout/stderr paths.
• docs/designs/axon-agent-design.md - Document the new transient default log location.
• packaging/deb/agent/default/axon-agent - Update the default config comments to describe where managed-process logs are written.

Added Files

N/A

Deleted Files

N/A

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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 expected. Profiles that explicitly configure stdout_log or stderr_log keep the existing configured path behavior.

Backward Compatibility

The default path for unmanaged stdout/stderr capture changes from the agent state directory to /tmp/axon-agent/logs. Agent APIs still report the effective log path in process state, and read_log continues to read from that path.

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Testing

Test Environment

• ROS Distribution: N/A
• OS: Local Axon development checkout
• Build Type: Standalone apps/axon_agent build

Test Cases

• Unit tests pass locally
• Integration tests pass locally
• E2E tests pass (if applicable)
• Manual testing completed

Full local CI was skipped at user request for this small agent/default-path change. Before committing this same diff, focused local validation was run successfully with:

cmake -S apps/axon_agent -B build-codex-agent -DAXON_AGENT_BUILD_TESTS=ON -DAXON_REPO_ROOT=/home/liuxy/ab_ws/axon
cmake --build build-codex-agent --target test_agent_service test_process_manager
ctest --test-dir build-codex-agent --output-on-failure -R 'test_agent_service|test_process_manager'

Manual Testing Steps

N/A

Test Coverage

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

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Screenshots / Recordings

N/A

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Performance Impact

• Memory usage: No change
• CPU usage: No change
• Recording 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

• Fixes N/A
• Related to N/A
• Refers to N/A

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Additional Notes

N/A

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Reviewers

N/A

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Notes for Reviewers

• Please review whether /tmp/axon-agent/logs is the right default location for transient managed-process stdout/stderr capture.
• Please verify deployments that need persistent managed-process logs can continue using explicit stdout_log and stderr_log profile settings.

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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)

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