fix(deeplink): preserve custom env fields when importing Claude providers

[thedavidweng]

Summary

When importing Claude providers through deeplinks (ccswitch://v1/import?...), custom environment variables were silently dropped. build_claude_settings constructed env from scratch with only known keys (ANTHROPIC_AUTH_TOKEN, ANTHROPIC_BASE_URL, model keys), discarding any user-defined variables like ANTHROPIC_CUSTOM_HEADERS or proxy settings.

The CLI/TUI provider creation path already preserved these fields by cloning existing settings — this fix brings the deeplink import path to parity.

Changes

src-tauri/src/deeplink/mod.rs

• Add custom_env: Option<Map<String, Value>> field to DeepLinkImportRequest

src-tauri/src/deeplink/provider.rs

• In merge_claude_config: collect non-standard env keys into custom_env
• In build_claude_settings: merge custom_env entries into the output env

Closes #261

[SaladDay]

@thedavidweng Thanks for the fix, this is a useful parity improvement.

I found one small blocker before merge: current main supports both Claude auth env keys, ANTHROPIC_AUTH_TOKEN and ANTHROPIC_API_KEY, but the deeplink merge path only reads/excludes ANTHROPIC_AUTH_TOKEN. So an inline config that only has ANTHROPIC_API_KEY can still fail with “API key is required”, or can end up with both auth env keys if apiKey is provided in the URL.

Could you update merge_claude_config to also read ANTHROPIC_API_KEY, add it to the known key list, and add a small deeplink import test for that case? After that I think this should be good to merge.