Extend .agents discovery to instructions, agents, and hooks for any opened folder

[mu88]

Feature

Please extend .agents as a first-class customization root for Copilot in VS Code, both for workspace folders and for user-level storage, even when the opened folder is not a Git repository.

This request is specifically about the .agents/ directory tree, not the root AGENTS.md file.

Current state

Related to the open tracking issue #292410, whose checklist already includes "Support other primitives (agents, hooks, instructions/rules, plugins) in .agents folder." This issue proposes a concrete, scoped design for that checklist item, plus the additional non-Git-folder guarantee. See also #322506 for the related agent-host/session-discovery configurability angle.

• Skills already support .agents/skills and ~/.agents/skills.
• Custom instructions currently cover .github/copilot-instructions.md, *.instructions.md, root AGENTS.md, and the .claude/.copilot instruction locations documented today, but not .agents/instructions.
• Custom agents currently use .github/agents, .claude/agents, and ~/.copilot/agents by default; note that [Feature Request] Allow configuring Copilot agent/skill/instruction discovery paths via settings #322506 indicates the agent-host/session-discovery layer already hardcodes .agents/agents and .agents/skills as workspace-level search roots on the SDK/session side, so this request is to make .agents an official, documented default consistently across both surfaces, not just a configurable or partially hardcoded one.
• Hooks are Preview. Default locations already include .github/hooks and the existing hook settings locations; .agents/hooks is not among them.

Proposed behavior

• Add .agents/instructions//*.instructions.md and ~/.agents/instructions//*.instructions.md as discovered locations.
• Add .agents/agents/ and ~/.agents/agents/ to the default agent-location set.
• Once hooks are stable enough for a default-path change, add .agents/hooks/ and ~/.agents/hooks/ alongside the existing hook locations.
• Discovery should work for any opened workspace folder, including non-Git folders.

Note: .agents/instructions, .agents/agents, and .agents/hooks can already be added manually today via chat.instructionsFilesLocations, chat.agentFilesLocations, and chat.hookFilesLocations. This request is to add them to the default sets, not to add net-new capability.

What a good solution would let me verify

• Opening a non-Git folder containing .agents (for example, D:\work\MyProjectOutsideGit) yields the same discovery behavior as a Git-backed folder.
• A workspace containing only .agents/instructions, .agents/agents, and (when hooks are no longer Preview) .agents/hooks behaves consistently without requiring .github / .copilot equivalents.
• Documented, deterministic handling for same-named files across same-scope roots where applicable.
• Existing .github / .claude / .copilot paths continue to work.

Why this helps

• One portable customization root across VS Code and Copilot CLI.
• Less duplication across .github, .claude, and .copilot.
• Better fit for teams that standardize on .agents in plain folders and monorepos, not only Git repos.

Related context

Skills already establish the .agents/ precedent; this request is to close the gap for instructions, agents, and hooks. If needed, this can be split into separate issues per artifact type.