NimsForest Issues

## Problem

`pkg/nim/` contains two distinct concerns:
1. **Messaging layer** (Wind, Leaf, Connect) — used by all services
2. **Agent layer** (Nim interface, Runner, 5A, Brain, Registry) — used only by nim implementations

Every service that just needs pub/sub imports the entire nim package. Pantheon has its own raw `nats.Connect()` because depending on a "nim" package for messaging doesn't make sense.

## Desired outcome

A new `pkg/wind/` package containing `wind.go`, `leaf.go`, `connect.go` with `package wind`. The `pkg/nim/` package imports `pkg/wind` and re-exports via type aliases for backwards compatibility.

## Key blocker: variable shadowing

The codebase uses `wind` as a local variable/parameter name in ~30 functions:
```go
func NewTree(cfg TreeConfig, wind *nim.Wind, ...) { ... }
```

When the package alias was `nim`, there was no conflict. But if the package name is `wind`, then `wind *wind.Wind` causes the parameter to shadow the package — making `wind.Leaf` (the type) inaccessible inside the function body.

## Required approach

Rename all local `wind` variables/parameters to `w` across ~16 files before switching the import. This is the structurally correct solution per Go convention but involves significant churn:
- ~30 function signatures change parameter name from `wind` to `w`
- All method calls inside those functions change (e.g. `wind.Drop()` → `w.Drop()`)
- All callers that pass the variable by name update accordingly

## Files that move to pkg/wind (Wind/Leaf only — 22 source + 10 test files)

cmd/forest/main.go, cmd/forest/cli.go, pkg/runtime/runtimecontroltreehouse.go, pkg/runtime/agent_brain.go, pkg/runtime/clubtreehouse.go, pkg/runtime/treehouse.go, pkg/runtime/tree.go, pkg/runtime/runtreehouse.go, pkg/runtime/processpublisher.go, pkg/agent/agent.go, pkg/dance/dance.go, internal/viewmodel/publisher.go, internal/sources/ceremony.go, internal/sources/factory.go, internal/windwaker/windwaker.go, internal/windwaker/dancer.go, internal/trees/songtree.go, internal/trees/persistencetree.go, internal/core/tree.go, internal/core/nim.go, internal/treehouses/interface.go, internal/songbirds/songbird.go

## Files that stay on pkg/nim (use Nim interface, Runner, Registry)

pkg/runtime/forest.go, pkg/runtime/nim.go, cmd/forest/scaffold.go

## After extraction

- Pantheon replaces raw `nats.Connect()` with `wind.Connect()` + `wind.Drop()`
- External services (nimsforestissue, hetznertreehouse, etc.) can migrate from `pkg/nim` to `pkg/wind` incrementally — aliases keep them working