feat: restructure .claude skills and add plugin marketplace support

[devin-ai-integration]

Summary

Restructures the .claude directory to follow the standardized Agent Skill format (matching the pattern in vlm-run/skills):

• Moved .claude/SKILL.md → .claude/skills/vlmrun-cli-skill/SKILL.md (content unchanged)
• Added .claude-plugin/marketplace.json — marketplace manifest listing the skill for remote installation
• Added .claude-plugin/plugin.json — plugin metadata (author, homepage, license, keywords)
• Added Claude Code installation instructions to README.md (new "### Claude Code" section)

This enables users to install the skill remotely via Claude Code:

/plugin marketplace add vlm-run/vlmrun-python-sdk
/plugin install vlmrun-cli-skill@vlm-run/vlmrun-python-sdk

Updates since last revision

• README step 3 now uses vlmrun config init / vlmrun config set / vlmrun config show instead of .env file setup, per reviewer feedback.
• Fixed source path in marketplace.json to ../.claude/skills/vlmrun-cli-skill (relative to .claude-plugin/) so it correctly resolves to the skill directory.
• Sorted JSON keys alphabetically to satisfy pretty-format-json pre-commit hook.
• Includes a minor black auto-format change in vlmrun/cli/_cli/chat.py (line-break in a typer.Option call, no behavioral change).

Review & Testing Checklist for Human

• Test remote installation end-to-end: Run /plugin marketplace add vlm-run/vlmrun-python-sdk and /plugin install vlmrun-cli-skill@vlm-run/vlmrun-python-sdk in Claude Code to verify the skill is discovered and installed correctly. This is the only reliable way to validate the plugin spec paths.
• Verify source path resolves correctly: The source field in marketplace.json is ../.claude/skills/vlmrun-cli-skill (relative to .claude-plugin/). Confirm this is the expected resolution behavior per the Claude Code plugin spec — it may need to be a repo-root-relative path instead.
• Verify vlmrun config CLI commands: The README references vlmrun config init, vlmrun config set, and vlmrun config show. Confirm these are the correct subcommands and syntax.
• Confirm naming convention: Both JSON files use "name": "vlmrun-cli-skill" — verify this matches expectations (the reference vlm-run/skills repo uses the bundle name "vlmrun-skills" rather than the individual skill name).

Notes

• The SKILL.md content is unchanged — this is purely a structural reorganization.
• JSON files are modeled after the .claude-plugin/ directory in vlm-run/skills.
• The chat.py formatting change is an unrelated pre-commit hook auto-fix (no logic change).

Link to Devin session: https://app.devin.ai/sessions/43313e807036481d8b77bea2228393f2
Requested by: @spillai

[devin-ai-integration]

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[spillai]

Recommend using vlmrun config instead of .env files.

[spillai]

Instead of setup via .env file, recommend the vlmrun config init and vlmrun config show/set

[devin-ai-integration]

Updated to use vlmrun config init / vlmrun config set / vlmrun config show instead of .env files.