feat(tools): implement M11 subagent system with task routing

Add tools-task crate with subagent registry and tool whitelist system:

Core Features:
- Subagent struct with name, description, keywords, and allowed tools
- SubagentRegistry for managing and selecting subagents
- Tool whitelist validation per subagent
- Keyword-based task matching and agent selection

Built-in Subagents:
- code-reviewer: Read-only code analysis (Read, Grep, Glob)
- test-writer: Test file creation (Read, Write, Edit, Grep, Glob)
- doc-writer: Documentation management (Read, Write, Edit, Grep, Glob)
- refactorer: Code restructuring (Read, Write, Edit, Grep, Glob)

Test Coverage:
- Subagent tool whitelist enforcement
- Keyword matching for task descriptions
- Registry selection based on task description
- Tool validation for specific agents
- Error handling for nonexistent agents

Implements M11 from AGENTS.md for specialized agents with limited tool access.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

crates/tools/task/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "tools-task"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+color-eyre = "0.6"
+permissions = { path = "../../platform/permissions" }
+
+[dev-dependencies]