Home.Agent: directory scaffolding for static subagents

[ludusrusso]

Parent PRD

#34

What to build

Extend the Home type with methods for managing static subagent directories. Each subagent gets a sub-Home at agents/<name>/ that provides the same accessors (Soul, Memory, CronsDir, CronResultsDir, etc.).

Acceptance criteria

• Home.AgentsDir() string returns path to agents/ subdirectory
• Home.Agent(name string) (*Home, error) returns a Home rooted at agents/<name>/, creating the directory if needed
• Home.ListAgents() ([]string, error) lists agent names by scanning agents/ directory
• Sub-Home accessors (Soul, Memory, CronsDir, CronResultsDir, SkillsDir) return correct paths under the agent's directory
• Agent name validation: alphanumeric + hyphens only, no path traversal
• Tests: creation, listing, round-trip identity files, directory accessors, name validation

Blocked by

None — can start immediately.

User stories addressed

• User story 13 (reuse Home abstraction)