feat(llamaswap): add llama-swaps (TLS) DSN scheme

llama-swap was http-only by DSN, pushing TLS-fronted instances onto the openai://
scheme (which loses the management/image methods). Add a "llama-swaps" scheme
that builds an https base URL, alongside "llama-swap" (http, local-first) —
mirroring redis/rediss. Both share one factory; llama-swaps is scheme-only (no
default built-in). The choice stays explicit because a DSN has no reliable
http-vs-https signal.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -159,15 +159,17 @@ m, _ := reg.Parse("m5/qwen3:30b,m1/qwen3:30b,thinking")
 ```
 
 DSN format: `scheme://[token@]host[/path]`, scheme ∈ `foreman`, `ollama`,
-`ollama-cloud`, `openai`, `anthropic`, `google`/`gemini`, `llama-swap`, or any
-scheme you add with `RegisterScheme`. The token is the credential (bearer token
-/ API key); the base URL is always `https://host[/path]` — except `llama-swap`,
-which builds `http://host[:port]` since it's local-first. `New()` loads `LLM_*`
-vars eagerly; unknown provider names also resolve lazily at Parse time
-(`my-prov/x` → `LLM_MY_PROV`).
+`ollama-cloud`, `openai`, `anthropic`, `google`/`gemini`, `llama-swap`,
+`llama-swaps`, or any scheme you add with `RegisterScheme`. The token is the
+credential (bearer token / API key); the base URL is always `https://host[/path]`
+— except `llama-swap`, which builds `http://host[:port]` since it's local-first
+(`llama-swaps` is the TLS twin → `https://host`, mirroring redis/rediss). `New()`
+loads `LLM_*` vars eagerly; unknown provider names also resolve lazily at Parse
+time (`my-prov/x` → `LLM_MY_PROV`).
 
 ```
-LLM_LS=llama-swap://token@box.local:8080   # then "ls/qwen3:14b" parses
+LLM_LS=llama-swap://token@box.local:8080    # http  → "ls/qwen3:14b" parses
+LLM_LS=llama-swaps://token@swap.example.com # https → TLS-fronted instance
 ```
 
 [llama-swap](https://github.com/mostlygeek/llama-swap) is a model-swapping proxy