feat: add Pi support and upstream provider presets

[SaladDay]

Summary

• add Pi as a first-class app across CLI, TUI, provider, prompt, session, usage, skill, and configuration workflows
• add Pi provider presets
• migrate the selected upstream built-in provider templates for Claude and Codex, preserving upstream field defaults and runtime behavior where applicable
• keep the TUI consistent with the existing application-family design

Scope

• includes DeepSeek, Zhipu GLM, Zhipu GLM en, ModelScope, MiniMax, Xiaomi MiMo, Xiaomi MiMo Token Plan (China), OpenCode Go, and OpenRouter presets for Claude and Codex
• excludes invitation links, affiliate/referral links, API-key registration links, and promotional content
• excludes the large DeepSeek official model catalog; generic native Responses behavior remains supported

Validation

• cargo fmt --check
• git diff --check
• provider template unit and integration tests
• Claude/Codex preset field parity tests
• reasoning-level catalog projection tests
• OpenCode Go Zen resolver and transform tests
• MiniMax/MiMo native Responses web-search tests
• provider_add_noninteractive integration test target: 22 passed

cargo clippy --lib --tests remains blocked by the pre-existing denied reversed_empty_ranges lint in src/cli/tui/ui/home_chart.rs:806; this PR does not modify that code.