Clarify agent architecture: small focused subtasks, not broad personas

- Remove product-manager agent (too broad, not being used)
- Update vision.md: agents are small, isolated, result-oriented
- Update CLAUDE.md: add Architecture section explaining skills/commands/agents

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

VISION.md

@@ -36,14 +36,21 @@ Skills don't do anything on their own. They're building blocks.
 
 ### Agents
 
-Agents combine multiple skills into specialized personas that can work autonomously.
+Agents are small, focused units that handle specific subtasks in isolated context.
 
-The `product-manager` agent combines issue-writing, backlog-grooming, and roadmap-planning skills to handle complex PM tasks. It can explore the codebase, plan features, and create well-structured issues—all with isolated context so it doesn't pollute the main conversation.
+Unlike commands (which run in the main conversation), agents are spawned via the Task tool to do a specific job and report back. They should be:
+- **Small and focused**: One clear responsibility
+- **Isolated**: Work without needing conversation history
+- **Result-oriented**: Return a specific output (analysis, categorization, generated content)
+
+Examples:
+- `code-reviewer`: Reviews a PR diff and reports issues
+- A hypothetical `categorize-milestone`: Given an issue, determines which milestone it belongs to
 
 Agents enable:
 - **Parallel processing**: Multiple agents can work simultaneously
-- **Context preservation**: Each agent maintains its own focused context
-- **Complex workflows**: Combine skills for multi-step tasks
+- **Context isolation**: Complex subtasks don't pollute the main conversation
+- **Reusability**: Same agent can be spawned by different commands
 
 ### Commands
 
@@ -51,11 +58,12 @@ Commands are the user-facing entry points—what you actually invoke.
 
 When you run `/plan-issues add dark mode`, the command:
 1. Understands what you're asking for
-2. Invokes the right agents and skills
-3. Guides you through the workflow with approvals
-4. Takes action (creates issues, PRs, etc.)
+2. References skills for knowledge (how to write issues, use Gitea, etc.)
+3. Optionally spawns agents for complex subtasks
+4. Guides you through the workflow with approvals
+5. Takes action (creates issues, PRs, etc.)
 
-Commands make the power of skills and agents accessible through simple invocations.
+Commands run in the main conversation context, using skills for knowledge and spawning agents only when isolated processing is beneficial.
 
 ## Target Users