feat(installer): GitHub Copilot targets — VS Code, Copilot CLI, JetBrains

[colbymchenry]

Summary

Adds GitHub Copilot as a supported agent for codegraph install / uninstall, via three new installer targets:

• copilot-vscode — Copilot Chat in VS Code. Writes the server entry to .vscode/mcp.json (local) or the VS Code User-dir mcp.json (global: ~/Library/Application Support/Code/User on macOS, %APPDATA%\Code\User on Windows, $XDG_CONFIG_HOME/~/.config/Code/User on Linux). Uses the servers key (not mcpServers) per VS Code's v1.102+ format, edits via jsonc-parser so user comments and sibling servers survive, and pins --path for local installs only. Global entries are deliberately variable-free (9769d6b): a user-level entry using ${workspaceFolder} makes VS Code toast "Variable workspaceFolder can not be resolved" in every folderless window; VS Code documents stdio cwd = workspace folder, and the server resolves the project via MCP roots with a cwd fallback, so no pin is needed.
• copilot-cli — the GitHub Copilot CLI (~/.copilot/mcp-config.json).
• copilot-jetbrains — the Copilot plugin in JetBrains IDEs (github-copilot config dir, XDG on Unix, %LOCALAPPDALOCAL%-fallback on Windows).

Also updates the TargetId union, registry, install/uninstall command descriptions, README, and CHANGELOG.

Testing

• npx vitest run __tests__/installer-targets.test.ts — 215 passed, 3 skipped (the skips are it.runIf(platform) variants for OSes other than the host; run on macOS).
• npx tsc --noEmit — clean.
• Platform-specific path resolution (APPDATA / XDG_CONFIG_HOME / macOS Application Support, plus unset-env fallbacks) is unit-tested with it.runIf(platform) gates. Validated on all three platforms — macOS (dev machine), Linux (node:22-bookworm Docker, run with --init), and Windows 11 ARM (Parallels VM, fresh clone at C:\dev\codegraph): 215 passed / 3 skipped on each, where the skips are the other platforms' gated variants — every gated test executed on its target OS.
• Note: this repo has no PR test CI, so these were manual runs against commit 490791c.
• Live detection verified on macOS — and it caught a real bug: the VS Code Copilot Chat extension writes lock files into ~/.copilot/ide/, so the CLI's existsSync(~/.copilot) check false-positived on a machine with only the VS Code extension. Fixed in 234dfe6 (the dir now only counts as a CLI footprint when it holds something besides ide, and uninstalling a from-scratch install deletes mcp-config.json rather than leaving a {} husk that would re-trigger detection). After the fix, the prompt on the same machine shows VS Code detected, Copilot CLI not found, JetBrains not found — all correct. Suites re-run green on macOS, Linux, and Windows at 234dfe6 (217 passed / 3 skipped each).

Validation checklist for reviewers

1. codegraph install --print-config copilot-vscode — inspect the snippet without writing files.
2. In a scratch project with a .vscode/ dir: codegraph install --target=copilot-vscode --location=local --yes, confirm .vscode/mcp.json gains servers.codegraph and pre-existing servers/comments are untouched.
3. Restart VS Code, check the server appears under MCP: List Servers.
4. codegraph uninstall --target=copilot-vscode --location=local --yes, confirm only the codegraph entry is removed.

🤖 Generated with Claude Code