v0.3.6

Support Claude Opus 5 read-only delegation (#306)

## Summary

- admit exact `claude-opus-5` only for local read-only Claude delegation
- preserve exact model binding through policy, launch, receipt, and
process checks without aliases, fallback, normalization, or retry
- keep mutating Stage A and fresh-Orb Claude pinned to exact
`claude-opus-4-8`
- add a maintained provider/executor readiness matrix for `/amux-claude`
and `/amux-pi`

## Validation

- `go test ./skills/amux-claude/experimental/claude-delegation -count=1`
- `go test ./scripts -count=1`
- `go test ./...`
- `go vet ./...`
- `go build ./cmd/amux`
- `git diff --check`

Closes #305