feat(smitebot): accept config file support to doctor and build

[Ashish-Kumar-Dash]

Summary

Follow-up to #116 , doctor and build now accept a campaign config file as a positional argument, replacing the need to pass paths manually via CLI flags.

CLI flags optionally override individual config values when provided:

 smitebot build campaign.toml
 smitebot build campaign.toml --target cln --coverage
 smitebot doctor campaign.toml
 smitebot doctor campaign.toml --aflpp-path ~/other

Overview

• Makes the campaign config file optional for doctor and build, users can run these commands with just CLI flags (e.g. smitebot build --target lnd --scenario encrypted_bytes) or with a config file where CLI flags override individual values
• When no config file is provided, --target and --scenario are required for build, --aflpp-path is required for doctor, and --smite-dir defaults to .
• Updated README examples to show both standalone and config-based usage

Ref. #70

[NishantBansal2003]

I think that if we want to preserve the flags, they should override the corresponding fields in the config. This would make the config required while allowing flags to override specific values when provided. It simplifies the model, aligns with many established CLIs, and avoids the overhead of determining which options are required or mutually exclusive, WDYT?

[morehouse]

Ready to merge after squash