fix: remove the unused power-of-ten rarity helper

[kitsuyui]

Summary

• remove the unused expectedPowersOfTen helper from src/rarity.ts
• remove the dedicated spec coverage for that dead helper
• rebuild dist/rarity.* so the published artifact matches the maintained source surface

Why

The production rules only use expectedSingleNonzeroDigitPrNumbers for pull request rarity. Keeping a separate unused helper and its dedicated test makes the maintained code and coverage inventory look larger than the reachable behavior.

Validation

• bun run lint
• bun run test
• bun run build

[github-actions]

gh-counter

PR gate

	Removed	Added	+/-
TODO/FIXME	0	0	0

Repo dashboard

	main (731d7b7)	#855 (279c836)	+/-
TODO/FIXME	0	0	0

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Reported by gh-counter

[github-actions]

🎉 Happy commit!

• dogfooding: PR fix: remove the unused power-of-ten rarity helper #855 always celebrates.
• dogfooding: 4b11ffa4d2db825efc7af80f9236e5796875a0b7 always celebrates.

[github-actions]

Code Metrics Report

	main (731d7b7)	#855 (279c836)	+/-
Coverage	97.1%	97.0%	-0.1%
Code to Test Ratio	1:1.5	1:1.6	+0.0
Test Execution Time	2s	2s	0s

Details

  |                     | main (731d7b7) | #855 (279c836) |  +/-  |
  |---------------------|----------------|----------------|-------|
- | Coverage            |          97.1% |          97.0% | -0.1% |
  |   Files             |              7 |              7 |     0 |
  |   Lines             |            177 |            171 |    -6 |
- |   Covered           |            172 |            166 |    -6 |
+ | Code to Test Ratio  |          1:1.5 |          1:1.6 |  +0.0 |
  |   Code              |            780 |            771 |    -9 |
- |   Test              |           1241 |           1234 |    -7 |
  | Test Execution Time |             2s |             2s |    0s |

Code coverage of files in pull request scope (100.0% → 100.0%)

Files	Coverage	+/-	Status
src/rarity.ts	100.0%	0.0%	modified

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Reported by octocov

[kitsuyui]

This pull request was created by an automated implementation attempt, but it did not satisfy the implementation contract and has been closed automatically.

Reason: implementation must record planning_contract_version 2

[github-actions]

gh-build-size

Target	main	#855	+/-
Total action artifacts	23,303,031 B	23,302,275 B	-756 B
Runtime bundle	1,153,987 B	1,153,904 B	-83 B
Source maps	17,133,019 B	17,132,428 B	-591 B
Type declarations	4,973,956 B	4,973,874 B	-82 B

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Reported by gh-build-size