docs: add installation guides for Zed and OpenCode

[jluocsa]

Summary

Adds two new installation guides under docs/installation-guides/ for MCP host applications that were missing documentation:

• install-zed.md -- the Zed editor.
• install-opencode.md -- the OpenCode terminal agent.

Both guides follow the established pattern of the existing installation guides (Cursor, Cline, Windsurf, Antigravity, etc.): prerequisites, remote-server-recommended path, local Docker path, verify steps, host-specific quirks, and troubleshooting.

Closes #2531.

Why these two

The two hosts have notably different MCP config shapes from the IDEs already covered, and both have shipped users hitting setup issues:

• Zed uses a context_servers settings key (not mcpServers), and expects command as a string plus a separate args array. It also introduced an mcp:<server>:<tool> permission key format in v0.224.0 that users need to know about to grant approval per-tool.
• OpenCode uses an mcp key with a required type discriminator ("local" / "remote"), command as a single array (executable + args), environment instead of env, automatic OAuth that needs "oauth": false to opt out, and a {env:VAR} string-interpolation pattern. The OpenCode docs specifically call out that the GitHub MCP server can blow the context window, so the OpenCode guide includes the per-agent tool-gating pattern recommended by their docs.

What's in the guides

Each guide covers:

• Remote server (recommended) using https://api.githubcopilot.com/mcp/ with a PAT in the Authorization header.
• Local server (Docker) using ghcr.io/github/github-mcp-server.
• Host-specific gotchas that I confirmed against the host's official docs (Zed's MCP docs and OpenCode's MCP servers docs).
• Verify steps using each host's actual UI / CLI commands (opencode mcp list, opencode mcp debug, Zed Agent Panel indicator dot).
• Troubleshooting for the most common configuration mistakes specific to each host.

Index/table updates

I also updated:

• docs/installation-guides/README.md -- added both hosts to the installation-guides index list and to the "Support by Host Application" table.
• README.md -- added both hosts to the "Install in other MCP hosts" (VS Code section) and "Install in Other MCP Hosts" (Claude section) lists.

Out of scope

• No code changes; docs-only.
• No tool-schema changes -- script/generate-docs does not need to run.
• Did not add UI deeplink-install buttons. Zed and OpenCode do not currently expose mcp-install deeplink schemes the way Cursor/VS Code do; the guides instead point at the Zed extension gallery (where a community-maintained GitHub MCP extension already exists) and OpenCode's standard config-file flow.

[Copilot]

Pull request overview

Adds missing documentation for installing/configuring the GitHub MCP Server in two additional MCP host applications (Zed and OpenCode), and wires those guides into the repo’s existing installation-guide indexes so they’re discoverable.

Changes:

• Added a new installation guide for Zed (context_servers config shape, remote + Docker local, verification, tool-permission notes, troubleshooting).
• Added a new installation guide for OpenCode (mcp config shape, remote + Docker local, verification/CLI commands, per-agent tool gating pattern, troubleshooting).
• Updated the top-level README and the installation-guides index README to include both hosts in lists/tables.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
README.md	Adds OpenCode/Zed links to the two “other MCP hosts” guide lists for discoverability.
docs/installation-guides/README.md	Adds OpenCode/Zed to the installation guide index and support matrix table.
docs/installation-guides/install-zed.md	New Zed-specific setup guide covering remote + local Docker configuration, verification, permissions, and troubleshooting.
docs/installation-guides/install-opencode.md	New OpenCode-specific setup guide covering remote + local Docker configuration, verification/CLI usage, per-agent tool gating, and troubleshooting.