feat(3.6.9): OpenCode Zen + Nous Research (Hermes) providers

Add two new model providers, both usable via API key or --subscription
(local CLI login, no key):

- opencode: OpenCode Zen gateway (OPENCODE_API_KEY, opencode.ai/zen/v1).
  Subscription mode drives the `opencode` CLI (`opencode run --auto`).
  Supports the Playwright MCP (--mcp): our .mcp.json is converted to
  OpenCode's own config schema and injected via OPENCODE_CONFIG.

- nous: Nous Research / Hermes models (NOUS_API_KEY,
  inference-api.nousresearch.com/v1). Subscription mode drives the
  `hermes` CLI (NousResearch/hermes-agent) on the user's Nous Portal
  OAuth login (`hermes setup --portal`), via `hermes chat -q`. No
  CLI-level MCP hook — falls back to Hermes's own built-in toolsets
  (web/terminal/computer-use).

Both wired into cli_binary_for, installed_cli_backends, cli_login_status
(prompt passed as argv, not stdin — neither CLI reads stdin for this).

Bump version 3.6.8 -> 3.6.9 across Cargo.toml, README, TUTORIAL, setup.sh,
install.ps1, and in-binary version strings. README/.env.example updated
with the new provider rows and subscription-login table.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HHFAVCHMvRkTy9Wgw7SayG

.env.example

@@ -51,6 +51,16 @@ TOGETHER_API_KEY=
 # openrouter:  https://openrouter.ai/keys
 OPENROUTER_API_KEY=
 
+# opencode:    https://opencode.ai/auth  (OpenCode Zen gateway)
+#              Or skip the key entirely and use --subscription with the
+#              `opencode` CLI logged into your own Zen/plan account.
+OPENCODE_API_KEY=
+
+# nous:        Nous Portal (https://portal.nousresearch.com) — Hermes models.
+#              Or skip the key entirely and use --subscription with the
+#              `hermes` CLI (`hermes setup --portal` for OAuth login).
+NOUS_API_KEY=
+
 # ollama:      local, no key needed. Override the endpoint if not default:
 #OLLAMA_BASE_URL=http://localhost:11434/v1