fix(router): calculateLocalRoutes must honor MinHops > 2

[0pcom]

Summary

The local route-calc fallback in `calculateLocalRoutes` only knows how to build 1-hop and 2-hop routes. When the global route-finder fails to produce a path (transient timeout, stale TPD, `ErrNoSuitableTransport`), `DialRoutes` falls back to `calculateLocalRoutes` — which would silently return a 2-hop route even when the caller demanded `min-hops >= 3`.

Empirical repro (against my visor)

call	requested	actual hops_count
`mux-bw --min-hops 3`	≥3	2 (wrong)
`mux-bw --min-hops 4`	≥4	2 (wrong)
`mux-bw --min-hops 5`	≥5	5 (correct — RF query succeeded, no fallback)

`cli route find -n 3 -x 3` and `-n 4 -x 4` both return proper 3-hop and 4-hop paths, confirming the route-finder service itself honors min-hops. The bug is purely in the local fallback.

Fix

```go
// Skip the 2-hop fallback when the caller demands >2 hops.
// calculateLocalRoutes only knows how to build 1-hop and 2-hop
// paths; returning a 2-hop path when min-hops>=3 was asked
// would silently violate the constraint.
if dialOpts != nil && dialOpts.MinHops > 2 {
return nil, nil, fmt.Errorf("local route calc cannot satisfy min_hops=%d (supports up to 2-hop only)",
dialOpts.MinHops)
}
```

The router's retry loop above will then either re-attempt the route-finder query or return the error to the caller — both correct behaviors when the local cache genuinely can't satisfy the constraint.

Test plan

• `go build ./...` clean
• `golangci-lint run` clean
• Live: `mux-bw --min-hops 3 ` reports hops_count >= 3 OR fails with a clean error message