Add infer and agents fields to Plan agent config and serialization

[digitarald]

Summary

Adds infer and agents fields to the Plan agent configuration, enabling control over subagent discovery and allowed subagents.

Changes

planAgentProvider.ts

• Add infer?: string and agents?: string[] to PlanAgentConfig interface
• Set defaults in BASE_PLAN_AGENT_CONFIG: infer: 'user', agents: []
• Add serialization in buildAgentMarkdown():
  • infer outputs as scalar value
  • agents uses same YAML array format as tools with proper quote escaping

agents.md (skill documentation)

• Document agents frontmatter field: agents: ["Agent1", "Agent2"] with semantics (omit = all, [] = none)

Behavior

• agents: [] disables subagent invocation for the Plan agent
• infer: 'user' enables user-scoped subagent discovery

[Copilot]

Pull request overview

Adds support for infer and agents frontmatter fields to the Plan agent configuration/serialization, and updates the custom agents documentation to describe the agents field.

Changes:

• Extend PlanAgentConfig with infer and agents fields and set defaults in BASE_PLAN_AGENT_CONFIG.
• Emit infer as a scalar and agents as a flow-style YAML array in buildAgentMarkdown().
• Document the new agents frontmatter field in the custom agents primitives doc.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/extension/agents/vscode-node/planAgentProvider.ts	Adds infer/agents to Plan agent config defaults and serializes them into generated .agent.md frontmatter.
assets/prompts/skills/agent-customization/primitives/agents.md	Documents agents frontmatter semantics and example usage.

Comments suppressed due to low confidence (2)

src/extension/agents/vscode-node/planAgentProvider.ts:102

• infer is emitted only when truthy (if (config.infer)), which will drop an explicit false value. If infer is meant to be a boolean frontmatter flag, this prevents generating infer: false to override the default behavior.

Suggestion: treat infer as boolean | undefined and emit it when it is explicitly set (e.g., check for !== undefined).

	if (config.infer) {
		lines.push(`infer: ${config.infer}`);
	}

src/extension/agents/vscode-node/planAgentProvider.ts:115

• New serialization behavior for infer/agents is introduced here, but the existing unit tests for buildAgentMarkdown don’t assert these fields (e.g., no case covering infer: false, infer: true, or agents: [] vs omitted). Adding targeted tests would help prevent regressions in YAML output formatting and semantics.

	if (config.infer) {
		lines.push(`infer: ${config.infer}`);
	}

	// Tools array - flow style for readability
	// Escape single quotes by doubling them (YAML spec)
	if (config.tools.length > 0) {
		const quotedTools = config.tools.map(t => `'${t.replace(/'/g, '\'\'')}'`).join(', ');
		lines.push(`tools: [${quotedTools}]`);
	}

	// Agents array - same format as tools (empty array = no subagents allowed)
	if (config.agents) {
		const quotedAgents = config.agents.map(a => `'${a.replace(/'/g, '\'\'')}'`).join(', ');
		lines.push(`agents: [${quotedAgents}]`);
	}