[Feature] Add CLI agent integration launch commands

[olegshulyakov]

Summary

Add an Integrations page that generates oMLX-style one-shot launch commands for supported CLI agents.
The first version should focus on commands shaped like:

'/Applications/oMLX.app/Contents/MacOS/omlx-cli' launch codex --model 'OmniCoder-9B-4bit' --api-key
'access-api-key'
'/Applications/oMLX.app/Contents/MacOS/omlx-cli' launch opencode --model 'OmniCoder-9B-4bit' --api-key
'access-api-key'
'/Applications/oMLX.app/Contents/MacOS/omlx-cli' launch pi --model 'OmniCoder-9B-4bit' --api-key
'access-api-key'

For llama-swap, the executable path should resolve to the appropriate packaged or local CLI path, but
the user experience should stay the same: select tool, model, API key, copy command, run agent.

User Story

As a local model user,
I want llama-swap to generate ready-to-run CLI agent launch commands,
so that I can start Codex, OpenCode, or Pi against my configured llama-swap models without hand-
writing tool-specific config.

Acceptance Criteria

• Given the user opens Integrations, when models are configured, then they can choose a model or
  alias.
• Given the user selects Codex, OpenCode, or Pi, then the UI generates a launch command using
  launch --model --api-key .
• Given model IDs, executable paths, or API keys contain spaces or punctuation, then generated
  shell commands quote arguments safely.
• Given no API key is entered locally in the browser, then the command shows a placeholder rather
  than exposing stored secrets.
• Given OpenAI and Anthropic integrations diverge later, then base URL rules remain explicit:
  OpenAI defaults to /v1, Anthropic defaults to server root when the client appends /v1/messages.
• Generated integration metadata is testable and does not call external services.

Developer Tasks

#	Task	Effort	Files / Modules
1	Define integration registry schema for launch commands, support level, API family, snippets, and base URL rules	M	proxy/, config/
2	Add initial registry entries for codex, opencode, and pi	S	proxy/
3	Add /api/integrations endpoint returning registry, models, aliases, base URLs, and resolved CLI executable	M	proxy/
4	Implement safe shell-quoting for executable path, model, and API key placeholders	S	proxy/
5	Add Integrations UI page with tool selector, model selector, API key input, command preview, and copy button	M	ui-svelte/
6	Add focused tests for registry validation, command rendering, and shell quoting	M	proxy/*_test.go

PRD.md
SPEC.md