Upgrade to TS7 for local type-checking (Stirling-Tools#6815)

# Description of Changes
We can't convert to TS7 completely yet because it lacks the TS API, so
ESLint and some of our scripts don't work, but we can do [what the TS
team suggest and run TS6 and TS7
side-by-side](https://devblogs.microsoft.com/typescript/progress-on-typescript-7-december-2025/#compiler).
When we do that, we take the `task frontend:typecheck:all` job from ~76s
to ~13s, and everything else continues to work as it did before.

I've set it so that CI will still use TS6 for the time being and locally
we use TS7 out of an abundance of caution because CI time doesn't really
matter but local time does. I do think it was a bit pointless doing that
since the TS team claim the type checking performs identically, but we
might as well have it like that for now. If it happens to go badly
locally for any devs, they can use `CI=true task frontend:typecheck` to
revert to use TS6 trivially.

Author: jbrunton96

.taskfiles/frontend.yml

@@ -295,64 +295,81 @@ tasks:
     cmds:
       - task: typecheck:proprietary
 
+  typecheck:_run:
+    internal: true
+    env:
+      CI: '{{ .CI | default "false" }}'
+    cmds:
+      - '{{ if eq .CI "true" }}npx tsc{{ else }}npx tsgo{{ end }} --noEmit --project {{.PROJECT}}'
+
   typecheck:core:
     desc: "Typecheck core build variant"
     deps: [prepare]
     cmds:
-      - npx tsc --noEmit --project editor/src/core/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: editor/src/core/tsconfig.json }
 
   typecheck:proprietary:
     desc: "Typecheck proprietary build variant"
     deps: [prepare]
     cmds:
-      - npx tsc --noEmit --project editor/src/proprietary/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: editor/src/proprietary/tsconfig.json }
 
   typecheck:saas:
     desc: "Typecheck SaaS build variant"
     deps:
       - task: prepare
         vars: { MODE: saas }
     cmds:
-      - npx tsc --noEmit --project editor/src/saas/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: editor/src/saas/tsconfig.json }
 
   typecheck:desktop:
     desc: "Typecheck desktop build variant"
     deps:
       - task: prepare
         vars: { MODE: desktop }
     cmds:
-      - npx tsc --noEmit --project editor/src/desktop/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: editor/src/desktop/tsconfig.json }
 
   typecheck:cloud:
     desc: "Typecheck cloud shared layer (standalone)"
     deps: [prepare]
     cmds:
-      - npx tsc --noEmit --project editor/src/cloud/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: editor/src/cloud/tsconfig.json }
 
   typecheck:scripts:
     desc: "Typecheck scripts"
     deps: [prepare]
     cmds:
-      - npx tsc --noEmit --project scripts/tsconfig.json
-      - npx tsc --noEmit --project editor/scripts/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: scripts/tsconfig.json }
+      - task: typecheck:_run
+        vars: { PROJECT: editor/scripts/tsconfig.json }
 
   typecheck:prototypes:
     desc: "Typecheck prototypes build variant"
     deps: [prepare]
     cmds:
-      - npx tsc --noEmit --project editor/src/prototypes/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: editor/src/prototypes/tsconfig.json }
 
   typecheck:portal:
     desc: "Typecheck developer portal build variant"
     deps: [install]
     cmds:
-      - npx tsc --noEmit --project portal/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: portal/tsconfig.json }
 
   typecheck:shared:
     desc: "Typecheck the shared design system"
     deps: [install]
     cmds:
-      - npx tsc --noEmit --project shared/tsconfig.json
+      - task: typecheck:_run
+        vars: { PROJECT: shared/tsconfig.json }
 
   typecheck:all:
     desc: "Typecheck all build variants"