fix: reject duplicate diagnostics provider names

[kang-heewon]

Fixes #700.

Summary

@croco/diagnostics-core now treats diagnostics provider names as unique within a DiagnosticsCollector. Re-registering the same provider instance remains idempotent, while registering a different provider with an existing name throws DuplicateDiagnosticsProviderProblem before the original provider can be overwritten.

변경 사항

• Added duplicate-name detection to DiagnosticsCollector.registerProvider().
• Added and exported DuplicateDiagnosticsProviderProblem using the existing Croco Problem pattern.
• Locked duplicate registration behavior with regressions for different-provider conflicts and same-instance idempotency.
• Documented the provider name uniqueness contract and added a patch changeset for @croco/diagnostics-core.

Verification

• pnpm vitest run src/tests/DiagnosticsIntegration.spec.ts --reporter verbose first failed before implementation with expected function to throw an error, but it did not.
• pnpm --filter @croco/diagnostics-core test - 1 file, 8 tests passed.
• pnpm --filter @croco/diagnostics-core typecheck - passed.
• pnpm --filter @croco/diagnostics-core build - passed.
• pnpm --filter @croco/diagnostics-core lint - 0 warnings/errors.
• node scripts/normalize-packages.mjs --check - passed.
• pnpm check - passed package manifest, docs catalog, circular dependency, oxlint, and oxfmt checks.
• CI=1 pnpm exec changeset status --since origin/trunk - passed with patch bump for @croco/diagnostics-core and dependents.
• git diff --cached --check - passed before commit.
• Pre-commit hook: oxfmt and oxlint passed.
• Pre-push hook: full pnpm test 197/197 tasks passed; full pnpm typecheck 196/196 tasks passed.

Self-review

• Correctness/regression: PASS. [diagnostics-core] 같은 이름의 diagnostics provider 등록이 조용히 덮어써짐 #700 acceptance is covered by the duplicate provider regression, which now throws before overwrite and verifies the original provider remains the only reported component. Same-instance re-registration is explicitly locked as idempotent.
• API/security/compatibility/release: PASS. The public API change is an additive Problem export, the new runtime dependency is the workspace @croco/problems-core package used by other Croco packages, no secrets or environment assumptions changed, and a patch changeset covers the publishable behavior.
• Maintainability/minimality: PASS. The behavior diff is limited to DiagnosticsCollector, one focused Problem class, package metadata, focused tests, docs, and release metadata. Independent review found no actionable issues.

Risk

Low. Consumers that accidentally registered two different providers with the same name will now fail fast instead of silently using the later provider. That is the intended behavior for #700.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 8bb3d17c-a509-44a5-afd1-6f305b410430

📥 Commits

Reviewing files that changed from the base of the PR and between 76bc0df and ae4c6dd.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (7)

• .changeset/diagnostics-provider-conflicts.md
• docs/troubleshooting/diagnostics.md
• packages/diagnostics-core/package.json
• packages/diagnostics-core/src/index.ts
• packages/diagnostics-core/src/libs/DiagnosticsCollector.ts
• packages/diagnostics-core/src/libs/problems/DiagnosticsProblems.ts
• packages/diagnostics-core/src/tests/DiagnosticsIntegration.spec.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/700-diagnostics-provider-conflicts

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[github-actions]

📊 Benchmark Results

❌ Some benchmarks failed

Benchmark	p75	Threshold	Baseline	vs Baseline	Status
CrocoApp benchmarks	3.4μs	-	-	-	⚠️
EventBusConfig.start (10 handlers)	1.5μs	-	9.0μs	-83.9%	✅
EventPublisher.publishNow single event	1.7μs	-	-	-	⚠️
DefaultHandlerResolver.resolve × 10	0.1μs	-	0.2μs	-60.0%	✅
Container.get singleton (cold)	1.0μs	-	0.5μs	+98.2%	❌
Container.register × 50 components	10.9μs	-	8.0μs	+36.0%	❌
Container.validate (50 components)	28.1μs	-	25.0μs	+12.4%	✅
Container.get singleton (warm)	0.4μs	-	0.3μs	+30.3%	❌
TelemetryRuntime benchmarks	1.9μs	-	2.0μs	-3.9%	✅

_{Updated: 2026-06-14T22:12:22.111Z · Commit: b2f2b26}