Material catalog: stop hardcoding (id → process, catalog name) in TS, expose from kernel

[ecto]

Problem

vcad-kernel-cost::Material::catalog() lives in Rust and is the source of truth for material density, price, machine rate, and process compatibility. But packages/app/src/stores/output-store.ts::MATERIAL_MAPPINGS (added on the v1 DFM branch) hardcodes a parallel TS table:

export const MATERIAL_MAPPINGS: Record<MaterialType, MaterialMapping> = {
  pla: { process: "fdm", catalogName: "PLA", display: { ... } },
  aluminum: { process: "cnc_3axis", catalogName: "Aluminum 6061", display: { ... } },
  steel: { process: "cnc_3axis", catalogName: "Steel 1018", display: { ... } },
};

Adding a new QuotePanel material now means editing both Rust (Material::catalog()) and TS (MATERIAL_MAPPINGS) and keeping them in lockstep. The display fields (lead time, friendly name) are arbitrary marketing strings that have no business being in TS specifically — they belong with the catalog entry.

Proposed approach

1. Extend vcad-kernel-cost::Material with optional UI metadata:

   pub struct Material {
       // existing physics + cost fields …
       /// Friendly display name shown in panels.
       #[serde(default)]
       pub display_name: String,
       /// Typical lead time in days for marketplace quoting.
       #[serde(default)]
       pub lead_time_days: u32,
   }

2. Add a Material::catalog_for(process: Process) -> Vec<Material> filter helper.
3. Expose via WASM: get_material_catalog(process: &str) -> JsValue.
4. QuotePanel calls getMaterialCatalog("fdm" | "cnc_3axis" | …) once and renders whatever the kernel returns. MATERIAL_MAPPINGS and MaterialType go away.

Why now

The catalog is going to grow (high-temp resins, more steels, exotic alloys for casting). Each new entry currently demands two PRs in lockstep. Before that surface area expands, fix the source-of-truth.

Side benefit

The MCP dfm_check and estimate_cost tools could accept any catalog material by name without a hand-maintained enum on the agent side.

Acceptance criteria

• Adding a material requires editing only vcad-kernel-cost.
• MATERIAL_MAPPINGS and MaterialType deleted from output-store.ts.
• QuotePanel renders the same set of options it does today, populated from the kernel.
• The 11 catalog entries (PLA, PETG, ABS, TPU, SLA Resin, Aluminum 6061, Steel 1018, Brass C360, Polycarbonate, Cast Aluminum A356, Cast Iron) all carry display + lead-time metadata.

References

• crates/vcad-kernel-cost/src/lib.rs::Material::catalog — current Rust catalog
• packages/app/src/stores/output-store.ts — current TS shadow table
• packages/app/src/components/QuotePanel.tsx::MATERIALS — consumer that becomes async-fetched