v3.0.0

Corrects the phoenix-thinking guidance on mount/3 vs handle_params/3.

The previous "Iron Law" said queries belong in handle_params/3 instead of mount/3 to avoid duplicate queries on initial load. That rationale is wrong: handle_params/3 also runs twice on initial load (dead render + connected render), so moving queries there does not dedupe anything.

What changed:

• Default is now to load data in mount/3. handle_params/3 is for data that changes on live navigation (push_patch / <.link patch={...}>), since mount does not re-run on patches
• For the actual initial double-load problem, the skill now lists the real tools with accurate descriptions: connected?/1 to gate work to the connected render, assign_async/3 to defer the load, and assign_new/3 to reuse conn.assigns set by upstream Plugs (it does not dedupe arbitrary mount work)
• Added a small connected?/1 code example
• Fixed the Red Flags entry that flagged any DB query in mount

Bumps:

• elixir plugin: 1.13.0 to 2.0.0
• marketplace: 2.0.0 to 3.0.0

Thanks to @khs-kks for digging this up in #9.