chore(prek): enable workspace hooks

[stdrc]

Summary

• split prek hooks by workspace project (root/kosong/kaos)
• install prek during make prepare and update docs

Testing

• prek hooks (format/check for kimi-cli/kosong/kaos)

[Copilot]

Pull request overview

This PR migrates the repository from pre-commit to prek for git hooks, enabling workspace-aware hook management. The migration splits hooks by workspace project so that only modified projects run their respective formatting and checking commands.

Key changes:

• Added install-prek target to Makefile that installs prek and sets up git hooks
• Created workspace-specific pre-commit configs for kosong and kaos packages with orphan mode
• Updated root pre-commit config to use project-specific make targets (format-kimi-cli, check-kimi-cli)
• Updated CONTRIBUTING.md documentation to reflect prek usage and workspace mode behavior

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Makefile	Added install-prek target and integrated it into prepare target to automatically install prek and hooks during setup
.pre-commit-config.yaml	Updated hook IDs and names to use project-specific targets (format-kimi-cli, check-kimi-cli) for the root workspace
packages/kosong/.pre-commit-config.yaml	Added orphan config for kosong package with hooks that run format-kosong and check-kosong from repo root
packages/kaos/.pre-commit-config.yaml	Added orphan config for kaos package with hooks that run format-pykaos and check-pykaos from repo root
CONTRIBUTING.md	Updated documentation from pre-commit to prek, explaining workspace mode and new installation process

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