feat(mcp-sync): sync GitHub Copilot CLI's MCP servers too

[opticon454]

Summary

MCP server sync (#521) copies MCP servers between the agent CLIs' own config files. GitHub Copilot CLI keeps its list too (~/.copilot/mcp-config.json), so it was left out. This adds it.

Copilot is not a Codeman run mode, so it has no CLI-registry entry (and giving it one would drag in launch, discovery and install). It is declared as plain data in src/mcp-sync-targets.ts (MCP_SYNC_ONLY_TOOLS) and joins the registry CLIs as a sync target, after them, so a registry CLI's definition wins a same-name difference. It takes part when copilot is installed or its config file exists, otherwise it is reported absent and never created. The same rules apply as for the others: additive only, switched-off servers are not copied, nothing unparseable is written, secrets keep the file 0600, results carry names only.

The dialect (copilot-json), checked against Copilot CLI 1.0.94

• File ~/.copilot/mcp-config.json, moved by COPILOT_HOME (verified: COPILOT_HOME=<dir> copilot mcp list reads <dir>).
• mcpServers, each entry with tools (["*"] = all), type local | http | sse, and command/args/env or url/headers. Copied servers are written with tools: ["*"]; an existing server's tool filter is never touched.
• copilot mcp disable does not mark the entry. It lists the name under disabledMcpServers in settings.json beside the config. Sync reads that list (never writes it), so a disabled server is not copied. If settings.json is not valid JSON the target is unreadable rather than guessed at.

Round trip checked with the real CLI: a file written by addServers('copilot-json', ...) is listed by copilot mcp list as fs (local), web (http), live (sse), and copilot mcp get fs shows the command, the masked env and Tools: * (all).

Tests

• test/mcp-sync.test.ts (+10): output captured from copilot mcp add; the written shape; existing server and tool filter kept; both directions between Copilot and Claude (sse expressed) and idempotent; a server disabled in settings.json is not copied (and the file is only read); a server disabled in Copilot but live elsewhere is still synced; invalid settings.json leaves the target unreadable without quoting the file; COPILOT_HOME; neither installed nor configured is absent; env values stay out of the result and the file is private.
• test/mcp-sync-targets.test.ts (+5): the declaration, the binary probe, yielding to a registry id, order in the route's targets, binaryOnPath.
• 537 tests across the registry, docs, guard, structure, schema and MCP suites pass; tsc --noEmit clean.

Docs: docs/cli-registry.md (new "Tools that are not run modes" paragraph), docs/api-reference.md, docs/wiki/Settings-Reference.md, the Settings text.

[Ark0N]

Merged and shipped in 1.41.0, thanks @opticon454! MCP server sync now includes GitHub Copilot CLI as a sync target, with all the same safety rules. One fix at merge: the route test didn't clear COPILOT_HOME, so on a machine with that set it wrote its fixture into the real Copilot config. It now clears the sync-only tools' relocation vars too, and Copilot's install probe in that test goes through the test's own installed set. I also added COPILOT_HOME to the docs that list the relocation vars. A per-target opt-out for Copilot would be a nice follow-up.