feat(desktop): packs-vs-teams design — deploy-to-channel and ownership model

[wpfleger96]

Context

PR #852 added full pack CRUD to the desktop UI. During review, two design concerns surfaced that are too large for that PR but need to be addressed:

1. Packs can't deploy to channel — teams can deploy all their personas to a channel in one click, but packs cannot. Users who install a pack still need to manually create a team from the pack's personas to deploy them together.

2. Pack ownership model is confusing — pack personas appear in "My Agents" alongside regular personas but behave differently (can't be individually deleted, delete error says "use Uninstall Pack"). The source_pack field on PersonaRecord controls lifecycle in ways that aren't visible in the UI.

Questions to resolve

• Should packs support a "Deploy to channel" action (like teams)?
• Should packs subsume teams entirely, or do they serve genuinely distinct purposes?
• Should source_pack prevent individual deletion, or be purely informational?
• If packs and teams merge: what's the migration path for existing teams.json data?

Current state

Dimension	Team	Pack
Purpose	"Quick deployment to channels"	"Bundled groups that can be installed and shared"
Deploy-to-channel	Yes	No
Versioned	No	Yes (semver)
Storage	teams.json (reference list)	Filesystem directory with manifest
Persona ownership	References free personas	Owns via source_pack field
Persona editability	Independently editable	Editable (as of #852)
Import method	.team.json file	Directory (native picker)
Export	Yes	No

Both are "groups of personas" displayed as card grids in the Agents view. The overlap is real — the question is whether to converge them or keep them distinct with clearer differentiation.