Make tsgo required when importing from .ts files

[milkyskies]

Currently tsgo is optional - when missing, the compiler silently falls back to unknown types for all TS imports. This leads to confusing downstream errors (unknown bindings, wrong type-only imports, missing type info in hover).

Proposal

When a .fl file imports from a .ts file and tsgo is not installed, emit a hard error:

error: tsgo is required to resolve TypeScript imports
  --> src/components/board.fl:8:1
   |
8  | import trusted { useJiraStore } from "../../stores/jira-store"
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: install with: npm i -g @typescript/native-preview

npm imports (from node_modules) could remain soft-warning since they have .d.ts files that can be parsed without tsgo.

Why not bundle tsgo

• Version coupling (tsgo is actively developed, would go stale)
• Binary size increase
• tsgo is a TS team project, not ours to redistribute