Include ref.parent matches in events by-reference navigation

[Copilot]

/events/by-ref/{referenceId} only matched reference:{id}, so clicking a Parent link failed when child events stored the relationship in ref.parent and no standalone parent event existed.

Changes

• Update both organization- and project-scoped by-reference handlers to match either reference:{id} or ref.parent:{id}.
• Add integration coverage for parent-only references in both endpoint scopes.
• Add HTTP samples for both by-reference routes.
• Merge the latest main and carry the behavior into the Minimal API EventHandler architecture.

Verification

• dotnet build --disable-build-servers -m:1 — passed with 0 warnings and 0 errors.
• GitHub Actions run 29467191099 — test-api, test-e2e, test-client, docker-build, and version passed.

Compatibility

• No route, response-contract, authorization, or persisted-data changes.
• Existing direct-reference matches remain supported; parent-reference matches are additive.

[CLAassistant]

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1 out of 2 committers have signed the CLA.

✅ niemyjski
❌ Copilot
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[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Exceptionless.AppHost	38%	39%	144	❌
Exceptionless.Core	72%	64%	8854	➖
Exceptionless.Insulation	23%	23%	205	❌
Exceptionless.Web	84%	67%	6841	✔
Summary	76% (21387 / 28148)	65% (9804 / 15158)	16044	✔