feat: add clawhub bundling automation to build workflow

[maxnoller]

Summary

• add scripts/bundle_clawhub_imports.mjs to automate conversion from skills.imports to bundled workspace/skills/<slug> content
• integrate bundling into build.sh via --bundle-imports and related flags, so migration can run as part of existing build flow
• document both integrated (./build.sh --bundle-imports ...) and standalone script usage in README.md

Why

• keep bundling aligned with existing build pipeline instead of a disconnected one-off script
• make persona migration and archive rebuild reproducible in one command
• reduce manual steps and drift risk for future updates

[Copilot]

Pull request overview

Adds an automation path to convert skills.imports entries that reference clawhub/<slug> into fully bundled skill directories under workspace/skills/<slug>, and integrates that migration into the existing packaging workflow.

Changes:

• Introduces scripts/bundle_clawhub_imports.mjs to download, extract, and materialize ClawHub skills locally and rewrite persona manifests.
• Extends build.sh with --bundle-* flags to optionally run bundling before packing .claw archives.
• Documents integrated and standalone bundling usage in README.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
scripts/bundle_clawhub_imports.mjs	New Node script to fetch + extract ClawHub skill zips and update manifest.json (skills.bundled / skills.imports).
build.sh	Adds CLI parsing and an optional pre-step to invoke the bundling script before building archives.
README.md	Adds usage docs for running bundling via build.sh or directly via the script.

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