Add Autohand Code CLI adapter

[igorcosta]

Summary

Adds an Autohand Code CLI adapter to agentic-stack.

The new adapter follows the existing manifest-driven harness pattern:

• installs an AGENTS.md entry point for Autohand project instructions
• mirrors .agent/skills/ into .autohand/skills/, which Autohand uses for project-level skills
• adds per-harness docs and README/getting-started references
• includes doctor detection and transfer-target aliases for autohand / autohand-code

Autohand Code CLI lives at https://github.com/autohandai/code-cli.

Validation

• python3 -m unittest tests.test_transfer_plan tests.test_transfer_cli tests.test_upgrade_manifest_doctor
• validated adapters/autohand-code/adapter.json through harness_manager.schema.validate
• built a transfer plan for move my memory into autohand and confirmed it targets autohand-code
• installed into a temp project with python3 -m harness_manager.cli autohand-code /tmp/agentic-stack-autohand-test --yes and verified AGENTS.md, .agent/install.json, and .autohand/skills were created

Note

Add autohand-code CLI adapter with detection, transfer, and documentation

• Adds a new autohand-code adapter that installs AGENTS.md to the project root and symlinks .agent/skills to .autohand/skills (with rsync_with_delete as fallback when symlinks are unavailable).
• Registers autohand-code in transfer_plan.py as a valid transfer target, with aliases autohand and autohand-code-cli.
• Adds detection in doctor.py using the presence of .autohand/skills as a strong signal.
• Updates install scripts, README, and getting-started docs to include the new adapter (adapter count: 12 → 13).

^{Macroscope summarized 43ae8e3.}