docs(skills): update Skills Overview for feed-synced subagents + archive distribution

[Aaronontheweb]

Part of #95 · Group 3 · UPDATE skills/overview.md · self-serve except one TODO

Scope: add feed-synced subagents (not just native metadata.subagent routing) and agents/.server-feeds/ sync; add archive-based resource distribution to the lifecycle phases; add a native-manifest pointer.

Also resolve: the unresolved <!-- TODO --> at ~line 109 (the system-skills list). Flag: that list needs a maintainer answer / the netclaw system-skill manifest — can't be sourced from code alone. Deps: #1, #2, #6.