[bot] Update Learning Hub for GPT-6 Astra, Vim mode GA, and new plugin CLI commands

[github-actions]

Summary

Reviewed the last 7 days of GitHub Copilot CLI releases (v1.0.83 → v1.0.84-5), GitHub Copilot app releases (v1.1.14 → v1.1.19), and VS Code Insiders release notes (1.138, Sept 1–8) for updates that affect the documented Learning Hub content (excluding cli-for-beginners, which is handled separately).

What was found

• GPT-6 Astra and continued Vim mode rollout in Copilot CLI: Vim mode (/vim, editorMode: vim) is now generally available to everyone (v1.0.84).
• New component-specific CLI commands (v1.0.84): copilot instruction list, copilot lsp list, and enable/disable on copilot plugin / copilot mcp / copilot skill, replacing the retired cross-kind copilot plugins --kind/--scope/--mcp/--skill flags. copilot skill add --project replaces copilot plugins install --skill --scope project.
• GitHub Copilot app: /goal command for persistent autopilot objectives (v1.1.15) with a live-status Goal pill, /settings slash command to jump to app settings (v1.1.16), and PR title/description/comment editing plus "Fix with instructions" (v1.1.18).
• VS Code 1.138 (Insiders): Agent Host sessions/chats now have shareable, browser-addressable links, and you can start a new session beside the current one.

Sections updated

• copilot-configuration-basics.md — added GPT-6 Astra to the model list, documented Vim mode GA, and added the new plugin/skill/instruction/LSP CLI commands with the related breaking-change notes.
• installing-and-using-plugins.md — cross-referenced the new component-specific enable/disable commands and the copilot skill add --project replacement.
• creating-effective-skills.md — updated the copilot skill CLI reference with --project and the breaking-change note for the retired --scope flag.
• github-copilot-app.md — added a new section covering /goal, /settings, and the PR editing / "Fix with instructions" features.
• agents-and-subagents.md — added a note on VS Code 1.138's shareable Agent Host session links and "new session beside" action.

All pages had their lastUpdated front matter bumped to 2026-09-12.

Source references

• https://github.com/github/copilot-cli/blob/main/changelog.md (v1.0.83–v1.0.84-5)
• https://github.com/github/app/blob/main/changelog.md (v1.1.14–v1.1.19)
• https://raw.githubusercontent.com/microsoft/vscode-docs/main/release-notes/v1_138.md

Warning

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The following domains were blocked by the firewall during workflow execution:

• code.visualstudio.com
• github.blog
• nishanil.github.io

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "code.visualstudio.com"
    - "github.blog"
    - "nishanil.github.io"

See Network Configuration for more information.

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