Remove duplicated Spring/Kotlin/Testing guidance from AGENTS.md files

[Copilot]

AGENTS.md files across the repo were re-stating guidance already covered in full by docs/SPRING.md, docs/KOTLIN.md, and docs/TESTING.md, creating maintenance overhead and inconsistency risk.

Changes

Root AGENTS.md — DO/DON'T section

Replaced 13 duplicated items (Kotlin idioms, Spring patterns, testing conventions) with a three-line blockquote pointing to the canonical docs. Kept only project-specific rules with no other home: AWS SDK v2/v1, JUnit 5/4, copyright year, sub-module dependency versions.

Root AGENTS.md — Error Handling section

Added a reference to docs/SPRING.md alongside the existing server/AGENTS.md pointer.

server/AGENTS.md

• Implementation Flow step 3: replaced inline "don't create new exception classes" rule with a link to docs/SPRING.md
• Error Handling section: removed the redundant S3Exception constants rule bullet; replaced with a reference to docs/SPRING.md (server-specific handler class names retained)

docs/TESTING.md — Conventions section

Removed Naming, Visibility, and Legacy-names bullets that verbatim restated docs/KOTLIN.md; the existing reference at the top of that section already covers them.

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[afranken]

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[Copilot]

Pull request overview

This pull request consolidates documentation by removing duplicated Spring, Kotlin, and testing guidance from various AGENTS.md files and creating a new canonical docs/SPRING.md reference. This reduces maintenance overhead and eliminates the risk of inconsistent documentation across the codebase.

Changes:

• Created docs/SPRING.md as the canonical reference for Spring Boot patterns, dependency injection, exception handling, and testing conventions
• Replaced 13 duplicated items in root AGENTS.md DO/DON'T section with references to docs/KOTLIN.md, docs/SPRING.md, and docs/TESTING.md
• Updated error handling sections in root and server/AGENTS.md to reference docs/SPRING.md
• Removed redundant bullets from docs/TESTING.md that were already covered by the existing reference to docs/KOTLIN.md

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
docs/SPRING.md	New canonical documentation for Spring Boot patterns including bean registration, dependency injection, controllers, configuration properties, exception handling, and testing guidelines
AGENTS.md	Replaced duplicated DO/DON'T guidance with references to canonical docs; updated error handling section to reference both docs/SPRING.md and server/AGENTS.md
server/AGENTS.md	Updated implementation flow and error handling sections to reference docs/SPRING.md instead of inline rules
docs/TESTING.md	Removed redundant naming, visibility, and legacy-names bullets that are already covered by the reference to docs/KOTLIN.md

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[Copilot]

The use of backticks around "@service" is ambiguous and potentially confusing. Line 7 explicitly states not to use "@service" annotations, but this line suggests delegating to a "@service". Consider changing this to "service class" or "service bean" without backticks to avoid confusion with the Spring @Service annotation.

Suggested change

	- All logic is delegated to a `@Service`; controllers call the service and return the result
	- All logic is delegated to a service class; controllers call the service and return the result

[afranken]

👍