refactor(mcp): extract registerTypedAppTool + typedAppSpec helper (KLA-419)

[jklaassenjc]

Summary

KLA-419 — surfaced during the 1.17.0 code-quality review.

After KLA-404 / KLA-405 / KLA-406 landed, the typed-input MCP App registration path was triplicated across apps_user.go, apps_device.go, apps_insights.go. Each was ~40 lines of identical mcp.Meta + wrap-fetch / errorResult / jsonResult + AddResource boilerplate. Every future typed MCP App would pay the same tax until extracted.

What changes

• typedAppSpec[In any] — mirrors appSpec for typed-input apps. Can't live in a []typedAppSpec slice (each In differs), but standardizes the per-app literal callers construct.
• registerTypedAppTool[In](s, spec) — wires the tool half with _meta.ui.resourceUri + the wrap-fetch / errorResult(spec.Name + ": ...") / jsonResult shape, plus the ui:// resource via the also-extracted registerUIResource helper. Future refactors of any of those subroutines now happen in one place.
• registerUIResource — factored out of registerAppResource so the typed path reuses the same 18 lines.

Migrations

registerUserView, registerDeviceView, registerInsightsView all collapse to a single typedAppSpec literal + helper call. Each register function dropped from ~40 lines to ~15.

One incidental wording change

insights_view used to emit "fetching insights: <err>" on handler failure; it now emits "insights_view: <err>" matching user_view / device_view. Same information; standardized for AI clients that correlate errors back to the calling tool. Pinned by TestRegisterTypedAppTool_ErrorMessagePrefixedWithToolName.

Test plan

• go test ./... full suite green (existing TestUserView_*, TestDeviceView_*, TestInsightsView_* cover the happy path through the helper end-to-end)
• go vet ./... clean
• New TestRegisterTypedAppTool_ErrorMessagePrefixedWithToolName locks the error-prefix contract
• Manually verified MCP tool count + _meta.ui unchanged for all four migrated/affected tools

Net diff

5 files changed, +140 / -127. The helper itself adds ~50 lines but each new typed app costs ~15 lines instead of ~40 going forward.

🤖 Generated with Claude Code

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Note

Low Risk
Mechanical refactor of MCP registration with one minor user-visible error string change for insights_view; behavior and metadata are intended to stay the same.

Overview
Introduces typedAppSpec[In] and registerTypedAppTool so typed MCP Apps (user_view, device_view, insights_view) register tools and ui:// resources from one spec literal instead of repeating meta, handler wrapping, and AddResource boilerplate in each file.

registerUIResource is factored out of registerAppResource so both no-args and typed apps share the same HTML + common.js injection path.

insights_view handler errors now use the insights_view: prefix (aligned with the other typed apps); previously they used fetching insights:. A new test locks that error-prefix contract.

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