Route the remaining perf sampling body through PlatformPlugin

[devin-ai-integration]

Problem

The Apple PlatformPlugin relocation is substantially complete, but CONTEXT.md still records one
remaining body-level branch: buildPerfResponseData in daemon perf handling.

Scope

• Move the remaining Apple/platform-specific perf sampling body behind the existing plugin-owned
  perf facet or a neutral perf contract below daemon.
• Preserve existing support-gate behavior and payload bytes.
• Add parity coverage that compares the old branch behavior across representative Apple, Android,
  web, and unsupported devices before deleting it.
• Remove the corresponding deferred note from CONTEXT.md only when the production call site is
  plugin-routed.

Constraints

• Do not expose daemon-owned types from the platform layer.
• Do not change public perf semantics or add new sampling metrics in this refactor.
• Keep Apple frame-health feature work separate.

Acceptance criteria

• buildPerfResponseData no longer contains the platform branch owned by the plugin.
• Table/facet parity and routing tests pass.
• Layering, typecheck, lint, focused perf tests, Fallow, and build pass.

Origin: CONTEXT.md deferred b.3 perf sampling body and post-#1174 architecture follow-up.

[devin-ai-integration]

Implementation session: https://app.devin.ai/sessions/4f6c547c71ac41a899c0ece81403bd6f

[devin-ai-integration]

Completed by #1191 (1f14e224d): perf sampling is routed through the PlatformPlugin facet with parity and shipped-path routing coverage.