Add agent role labels, task notes, and blocked status

[davidewheeler9-spec]

Summary

• Role label — each agent can be assigned a custom name (e.g. "Codex Engineer") shown in the ToolOverlay
• Task note — a one-line description shown below the role when the agent is selected
• Blocked toggle — manual amber ⊗ status flag that coexists with auto-detected JSONL status (Working/Idle/Waiting)
• Inline edit UI — clicking a selected character reveals role/note/blocked fields editable in-place; pencil buttons open input fields, Enter/blur confirms
• Persistence — roles stored in workspaceState under pixel-agents.agentRoles, restored on webview reload and VS Code restart
• Decoupled click behavior — clicking a character now only selects it (shows overlay); a new ⌨ button in the overlay header focuses the terminal explicitly, so input fields remain usable

Test plan

• Click "+ Agent" to create agents — characters appear in office
• Click a character → overlay appears without focusing the terminal
• Type a role name → press Enter → role persists in overlay
• Add a task note → blur → note persists
• Click "○ Blocked" → toggles to amber "⊗ Blocked" indicator in overlay header
• Click ⌨ button → Claude terminal gains focus
• Reload webview → roles/notes/blocked status all restored correctly
• Close and reopen VS Code → roles persist across sessions

🤖 Generated with Claude Code