Share one TypeScript program in server-fn surface tests

[isuttell]

Summary

server-fn-surface-test-helpers.test.ts rebuilt a control-panel TypeScript Program on every case. That sat near vitest's 5s default under runner contention and made hosted Verify flake on unrelated PRs.

This PR builds the program once in beforeAll and reuses it across cases. Assertions and helper behavior are unchanged. @splitch/stats is a different shape (one-off dynamic import), so it is not included.

Changes

• Collect every probe fixture into one overlay map
• Create a single sourceProgram in beforeAll
• Reuse createServerFnSurfaceDiscovery for all cases

Risk: LOW

• Areas touched: control-panel surface-discovery unit tests only
• Security: none
• Performance: removes repeated TypeScript program construction
• Breaking: none

Test plan

Recorded on head f338e6a5 (Node v24.17.0, pnpm 11.8.0).

• Shared-program file green under control-plane-api workers-pool contention, 3 times:

  cd apps/control-plane-api && pnpm exec vitest run --config vitest.config.workers.ts
  pnpm --filter @splitch/control-panel exec vitest run --config vitest.config.ts \
    src/lib/testing/server-fn-surface-test-helpers.test.ts

  Wall 2506ms / 1976ms / 2058ms; vitest 1.88s / 1.36s / 1.41s; 13/13 each (tests 1373ms / 923ms / 981ms)
• Control-panel suite ×3 (parallel full-package verify of the file's workspace):

  pnpm --filter @splitch/control-panel test

  38.437s / 38.264s / 38.696s; 163 files / 1400 tests; surface file 989ms / 826ms / 1082ms
• pnpm verify:ci --force green: 106/106, 8m25.935s (507048ms); surface file 5076ms under the full parallel graph (first case 503ms)
• Hosted Verify green on f338e6a5 (run 35134277209)

Issue: SPL-386

Linear Issue: SPL-386

  

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