Restructures the Rust codebase into a self-contained clawcode workspace
under rust/clawcode, collocating claw config (agents, skills) with the
Rust crates. Follows the project convention of keeping source under rust/.
- Move crates: agents, api, claw-cli, commands, compat-harness,
migrate-patch-names, mock-anthropic-service, plugin-types, plugins,
runtime, telemetry, tools
- Drop the old flat rust crates tree
- Add claw/ workspace config with agents and skills
- Gitignore local .env secrets (claw/.env, claw/.env_deepseek)
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