test(perf): add plugin init regression budget

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/__tests__/perf/fixtures/in-tree/AGENTS.md

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+# fixture root

src/__tests__/perf/fixtures/in-tree/packages/pkg-one/AGENTS.md

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+# fixture package

src/__tests__/perf/fixtures/in-tree/packages/pkg-one/src/file-16.ts

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+export const file16 = 16

src/__tests__/perf/fixtures/in-tree/packages/pkg-one/src/file-17.ts

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+export const file17 = 17

src/__tests__/perf/fixtures/in-tree/packages/pkg-one/src/file-18.ts

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+export const file18 = 18

src/__tests__/perf/fixtures/in-tree/packages/pkg-one/src/file-19.ts

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+export const file19 = 19

src/__tests__/perf/fixtures/in-tree/packages/pkg-one/src/file-20.ts

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+export const file20 = 20

src/__tests__/perf/fixtures/in-tree/src/AGENTS.md

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+# fixture src

src/__tests__/perf/fixtures/in-tree/src/app/file-01.ts

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+export const file01 = 1

src/__tests__/perf/fixtures/in-tree/src/app/file-02.ts

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+export const file02 = 2

src/__tests__/perf/fixtures/in-tree/src/app/file-03.ts

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+export const file03 = 3

src/__tests__/perf/fixtures/in-tree/src/app/file-04.ts

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+export const file04 = 4

src/__tests__/perf/fixtures/in-tree/src/app/file-05.ts

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+export const file05 = 5

src/__tests__/perf/fixtures/in-tree/src/app/file-06.ts

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+export const file06 = 6

src/__tests__/perf/fixtures/in-tree/src/app/file-07.ts

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+export const file07 = 7

src/__tests__/perf/fixtures/in-tree/src/app/file-08.ts

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+export const file08 = 8

src/__tests__/perf/fixtures/in-tree/src/app/file-09.ts

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+export const file09 = 9

src/__tests__/perf/fixtures/in-tree/src/app/file-10.ts

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+export const file10 = 10

src/__tests__/perf/fixtures/in-tree/src/lib/file-11.ts

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+export const file11 = 11

src/__tests__/perf/fixtures/in-tree/src/lib/file-12.ts

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+export const file12 = 12

src/__tests__/perf/fixtures/in-tree/src/lib/file-13.ts

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+export const file13 = 13

src/__tests__/perf/fixtures/in-tree/src/lib/file-14.ts

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+export const file14 = 14

src/__tests__/perf/fixtures/in-tree/src/lib/file-15.ts

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+export const file15 = 15