Refactor: Automate Rust-to-TypeScript generation using ts-rs

[mmogr]

Problem

Manual synchronization between Rust backend types and TypeScript frontend interfaces is fragile and error-prone. The recent regression in #151 (commit e1af0cd) occurred because #[serde(rename_all = "camelCase")] was added to Rust structs but the TypeScript interfaces weren't fully updated to match.

Proposed Solution

Replace manual TypeScript interface synchronization with automated ts-rs generation to prevent serialization mismatches.

Why ts-rs?

• ✅ Works seamlessly with existing serde attributes (respects rename_all = "camelCase")
• ✅ Generates TypeScript via derive macro at compile time
• ✅ Minimal runtime overhead (generation happens during build)
• ✅ Generates .d.ts or .ts files directly into src/types/ directory
• ✅ Handles Rust type mappings well (Option → ?, Vec → [], etc.)

Implementation Tasks

1. Add ts-rs dependency

Add to crates/gglib-gui/Cargo.toml:

[dependencies]
ts-rs = "7.1"  # or latest stable

2. Update Rust structs

In crates/gglib-gui/src/types.rs, add #[derive(TS)] to all API types:

use ts_rs::TS;

#[derive(Debug, Clone, Serialize, Deserialize, TS)]
#[ts(export, export_to = "../../../src/types/generated/")]
#[serde(rename_all = "camelCase")]
pub struct GuiModel {
    // ... fields
}

Apply to:

• GuiModel
• StartServerRequest
• ServerHealthStatus
• GuiSettings
• HfToolSupportResponse
• Any other types exposed via API

3. Configure generation

• Types generate to src/types/generated/ on cargo build
• Check generated files into git for visibility
• Update .gitignore if needed (consider tracking generated files for transparency)

4. Update TypeScript imports

Replace manual interfaces in src/types/index.ts:

// Before:
export interface GgufModel { /* manual sync */ }

// After:
export { GuiModel as GgufModel } from './generated/GuiModel';
// Or extend if needed:
export interface GgufModel extends GuiModel { /* client-only fields */ }

5. Add CI validation

Add check to CI pipeline:

# Verify generated types match committed files
cargo build --package gglib-gui
git diff --exit-code src/types/generated/

Fails if developers forget to regenerate types after Rust changes.

6. Documentation

Update CONTRIBUTING.md or docs/ARCHITECTURE.md:

• Explain ts-rs workflow
• Document when/how types regenerate
• Note that Rust structs are source of truth

Benefits

• Compile-time type safety across Rust/TS boundary
• Automatic camelCase conversion via existing serde attributes
• Prevents regressions like Bug: GUI displays NaN/Missing data due to serialization mismatch #151 at build time
• Single source of truth for API contracts
• Zero runtime cost (generation at compile time)

Trade-offs

• Generated files add noise to git diffs (mitigated by separating to generated/)
• Build process couples frontend types to Rust compilation
• Developers must run cargo build before frontend work (document in README)

Related Issues

• Fixes root cause of Bug: GUI displays NaN/Missing data due to serialization mismatch #151 (serialization mismatch)
• Prevents similar issues with future backend changes

Alternative Considered

specta: More runtime-focused, better for tRPC-style workflows. Overkill for this project's simpler HTTP API pattern.