Split translation providers into six presets; fix popup version

[ycosine]

What changed

The provider picker now offers six providers instead of three:

Provider	Kind	Required config	Default model
Google	free endpoint	—	—
DeepL	REST	API key	—
Anthropic (new)	native Claude Messages API via @anthropic-ai/sdk	API key	claude-opus-4-8 (editable)
DeepSeek (new)	chat-completions, pinned to api.deepseek.com	API key	deepseek-chat (editable)
OpenAI (new)	chat-completions, pinned to api.openai.com/v1	API key	gpt-4o-mini (editable)
Custom	any OpenAI-compatible endpoint	base URL + model + key	—

Anthropic provider

• Built on the official @anthropic-ai/sdk (browser mode in the MV3 service worker; host permission scopes the origin)
• Streams via the Messages API SSE and feeds the existing TR_TRANSLATE_PARTIAL pipeline, so Claude subtitle translations render token-by-token like DeepSeek
• No temperature sent (removed on Opus 4.7+ — would 400); typed SDK error classes mapped to the existing TranslationError codes; refusal stop reason surfaced as an error instead of an empty translation
• Validation uses the free count_tokens endpoint (checks both key and model id)
• Default model is claude-opus-4-8; for faster/cheaper subtitle translation users can set claude-haiku-4-5 in the model field

DeepSeek / OpenAI presets

• Implemented as configurations of the existing chat-completions core (streaming, JSON fallback, retry/backoff all inherited)
• Base URL is pinned by the preset and no longer part of the credential form; model is prefilled and editable
• Existing users on "OpenAI-compatible" (now labeled Custom) keep working unchanged — same stored id, same credentials

Misc

• Popup readiness/summary logic understands fixed-endpoint presets (key-only = ready)
• New glyphs for Anthropic / DeepSeek / Custom in popup and options
• Host permissions: api.anthropic.com, api.deepseek.com, api.openai.com
• Popup version fix: header showed a hardcoded v0.1; it now reads chrome.runtime.getManifest().version

Validation

• pnpm type-check, pnpm lint, content-script tests (25), pnpm build all green; built manifest carries the new host permissions and the popup bundle no longer contains the hardcoded version
• Mock-fetch harness: DeepSeek requests hit the pinned URL with the default model (and honor a model override); Anthropic provider exercised through the real SDK against a mocked Messages API for both non-streaming and SSE streaming paths (partials + final text correct, no temperature in the request body)
• Not yet run against live Anthropic/DeepSeek/OpenAI keys — worth a smoke test of the Options "Test" button per provider before release

🤖 Generated with Claude Code