feat(cli): implement local persistent state for agent tracking

[Kayd-06]

📋 Summary

Implements a JSON-based local persistence layer for the MoFA CLI. Agents started via mofa agent start are now recorded to a local state file so that mofa agent list can display real data instead of hardcoded mock entries.

🔗 Related Issues

Closes #227

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🧠 Context

The mofa agent commands (list, start, etc.) currently use hardcoded mock data, making it impossible to track agent lifecycle across terminal sessions. This is a prerequisite for functional CLI-based agent management.

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🛠️ Changes

• Added [crates/mofa-cli/src/utils/state.rs] CliState struct with JSON load/save and corruption recovery (renames to state.json.bak)
• Updated agent start to persist agent metadata on invocation
• Updated agent list to read from the local state file
• Added chrono dependency for timestamps and uptime calculation

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🧪 How you Tested

1. cargo test -p mofa-cli -- utils::state (2 unit tests pass)
2. cargo run -p mofa-cli -- agent start test-agent
3. cargo run -p mofa-cli -- agent list (verified agent appears with uptime)

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⚠️ Breaking Changes

• No breaking changes
• Breaking change (describe below)

If breaking:

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🧹 Checklist

Code Quality

• Code follows Rust idioms and project conventions
• cargo fmt run
• cargo clippy passes without warnings

Testing

• Tests added/updated
• cargo test passes locally without any error

Documentation

• Public APIs documented
• README / docs updated (if needed)

PR Hygiene

• PR is small and focused (one logical change)
• Branch is up to date with main
• No unrelated commits
• Commit messages explain why, not only what

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🧩 Additional Notes for Reviewers

Clippy Notes

cargo clippy was executed across the workspace. Pre-existing warnings are present in mofa-kernel, but this PR does not introduce any new warnings.

This PR tracks logical CLI state only. OS-level process management (PID monitoring, daemonization) is explicitly out of scope.
State file location: %APPDATA%/mofa/state.json (Windows).

[lijingrs]

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