docs: add AGENTS.md contributor guidance

[Darius B. (journaltraces)]

Summary

Adds a repository-root AGENTS.md with concise guidance for AI coding assistants contributing to Semantic Kernel.

The guide covers:

• repository and language routing for .NET, Python, and Java
• relevant source and test locations
• build, test, and formatting commands
• guidance for connectors, plugins, memory, and vector-data changes
• API compatibility and cross-language considerations
• security and secret-handling reminders
• focused validation guidance before opening a PR

The document intentionally complements CONTRIBUTING.md rather than duplicating the contributor workflow.

Fixes #14028

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds an AGENTS.md guide intended to help AI coding assistants (and contributors) navigate the repo layout and follow contribution/testing expectations.

Changes:

• Introduces an AGENTS.md “start here” checklist and repository map for .NET/Python/Java.
• Documents build/test/format commands and general guidance for connectors/plugins/API compatibility/security.
• Adds pre-PR validation reminders (git diff checks, avoiding secrets, keeping diffs focused).

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[github-actions]

MAF Automated Review — Iteration 1

Result: Findings reported
Scope: full PR (1 commit(s)): 23e42d325764
Model: claude-opus-4.8

Overview

This is a docs-only change adding a single repository-root AGENTS.md (154 lines) that
navigates AI coding assistants through the .NET/Python/Java layout, build/test commands,
and secrets posture, while explicitly deferring to CONTRIBUTING.md as the source of truth.
Every path, cross-file reference, and command semantic was verified against the frozen
checkout and is accurate; there is no executable, security, or trust-boundary surface. The
one residual accuracy gap is that the documented .NET build command is Windows-only
(build.cmd) even though the repository ships an equivalent dotnet/build.sh, which would
misdirect the file's primary Linux/macOS audience.

Reviewed the supplied pull-request change set across correctness, security/reliability, architecture, and failure behavior.
1 verified finding remained after source verification (1 medium) across 1 file. Details are attached to the affected lines below.

Affected areas: AGENTS.md

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.