feat(codebuddy): add CodeBuddy Code agent support

[Kayphoon]

Summary

• Adds first-class CodeBuddy Code support via rtk hook codebuddy and rtk init --agent codebuddy.
• Supports both project-local .codebuddy/settings.json hooks and the global CodeBuddy App/IDE marketplace plugin path.
• Adds clean install/uninstall behavior with docs and tests.

Why

This is an expanded implementation for #1966. It covers the CLI/settings hook path plus the CodeBuddy App/IDE plugin install path, including enabledPlugins handling. Related PR #1967 covers a smaller global settings integration; this PR is intended as the complete CodeBuddy agent support surface.

Changes

• Adds CodeBuddy CLI dispatch for rtk hook codebuddy, rtk init --agent codebuddy, and uninstall handling.
• Reuses the Claude-compatible PreToolUse command rewriting flow while leaving permission approval to the CodeBuddy host.
• Adds project/global settings patching, dry-run/manual patch output, plugin manifest and hook generation, idempotent install behavior, and uninstall cleanup.
• Updates README, hook documentation, and the supported agents guide for CodeBuddy.

Review Guide

Start with src/hooks/init.rs for install, plugin, and uninstall behavior. Then check src/hooks/hook_cmd.rs for the hook protocol output and src/main.rs for CLI dispatch. The docs changes mirror the new user-facing commands and can be reviewed after the behavior.

Test plan

• cargo fmt --all --check
• cargo test codebuddy
• cargo test --all
• cargo clippy --all-targets
• Manual temporary-HOME install/uninstall check for rtk init -g --agent codebuddy, including plugin files, enabledPlugins, idempotent reinstall, and cleanup of generated config.

Risk

Risk level: Medium.

Potential impact is localized to CodeBuddy config generation and CodeBuddy hook output. Existing agent integrations and telemetry paths are not changed.

Rollback plan: revert this commit.

Linked Issues

Closes #1966

Related: #1967