D676 — GitHub Copilot CLI is a provider, with a hook file of its own

Decision. copilot (provider id copilot, "GitHub Copilot CLI"; not Copilot in VS Code) is a provider with all five global cells: ~/.copilot/mcp-config.json, copilot-instructions.md, skills/<name>/, agents/<name>.agent.md and cartographer-hooks/<name>/. A hook is registered as its own file ~/.copilot/hooks/cartographer-<name>.json, returned as a managed file (the hook's own files are kept out of hooks/, which Copilot parses recursively: a non-Copilot JSON there logs an error at every session start) so a prune deletes it (the OpenCode plugin pattern); ~/.copilot/settings.json is never patched. Only SessionStart, PreToolUse and PostToolUse are registered. In a workspace only AGENTS.md and .agents/skills/ are projected; project mcp, agent and hook are unsupported. Paths are $HOME/.copilot: COPILOT_HOME is not honoured.

Why. Every cell was probed on 1.0.94 with COPILOT_HOME on a scratch directory. The project mcp, agent and hook locations are documented but were not observed working without folder trust, and a destination is declared, never invented. Copilot has no hook matcher, so a hook that declares one cannot keep its meaning: it is installed and not registered, with a warning. The write-findings hook therefore declares none for Copilot and filters on the tool name in its command (<server>-<tool>); its channel is --channel copilot, {"additionalContext": …} at the top level of stdout, exit 0. The MCP entry needs "tools": ["*"], or a non-interactive session is offered no tool.

Alternatives rejected. Patching settings.json inline hooks: it carries the user's own configuration, and a dedicated file is owned whole. Registering a matcher hook anyway: it would fire for every tool. Honouring COPILOT_HOME: no provider reads a home override today, and one provider doing so would split the base-dir rule. Counting MCP calls in usage: they name no managed artifact, so only skill activations are read.

Consequences. The connect form listed Crush without being able to select it (formProviders lacked it, so its toggle wrote nothing); both are now in the list and a test pins every agent field to its provider. The textual textResultForLlm carries a second JSON object after the response with no separator, which the findings parser already decodes value by value. Hook events, a matcher and the project cells are added by a probe, not by analogy.