feat(basectl): automatic devnet detection

[0xEdmundo]

Closes #34

What changed?

Added automatic devnet configuration detection when -c devnet is passed to basectl.

Implementation

• When basectl -c devnet is called, it searches for .devnet/basectl.yaml starting from the current directory and traversing up to parent directories
• If found, loads the configuration from that file
• If not found, returns a helpful error message

How to test

1. Run just devnet in the base/base repo to start devnet
2. Create .devnet/basectl.yaml with your config
3. Run basectl -c devnet to verify auto detection works

Tests

• Added test_devnet_config_not_found test
• All existing tests pass (3/3)

[cb-heimdall]

🟡 Heimdall Review Status

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