docs: add AGENTS.md and CLAUDE.md for AI coding agents

Motivation:
AI coding agents benefit from project-specific instructions to follow
conventions, run correct validation, and produce consistent PRs.

Modification:
Add AGENTS.md with comprehensive rules (worktree, licensing, PR,
formatting, validation, test, code, CI, commit format) and CLAUDE.md
with a pre-PR verification checklist.

Result:
AI agents working on this repository will follow established
conventions and produce higher-quality contributions.

Tests:
Not run - docs only

References:
None - AI agent configuration

Author: He-Pin

AGENTS.md

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+# Agent Rules for Apache Pekko Samples
+
+If this file conflicts with community conventions, update this file.
+
+## Worktree Rules
+
+- Base new work on `origin/main` unless the user or maintainer requests another branch.
+- Keep every PR scoped to one change.
+- Do not mix behavior changes, formatting churn, dependency updates, and unrelated cleanup.
+- Do not revert user changes or unrelated local changes.
+- Use `rg` or `rg --files` for repository searches.
+- Read neighboring code before editing.
+- Preserve existing license and copyright notices.
+- Do not add `@author` tags.
+- Follow the Licensing Rules below for every new file.
+
+## Project Structure
+
+- Each sample is a standalone sbt project in its own directory (e.g., `pekko-sample-cluster-java/`).
+- Each sample has its own `build.sbt` and `README.md`.
+- Samples come in Java and Scala variants where applicable.
+- The `docs-gen/` directory generates documentation from samples.
+
+## Licensing Rules
+
+- Do not hand-write or invent license headers. Let sbt manage them.
+- For new files, run `sbt headerCreateAll` to add the correct header. Do not manually paste header text.
+- Existing files with copyright statements must keep those copyright statements intact. Never delete or rewrite an existing copyright notice; only add information.
+- New files containing new code must use the standard Apache license header.
+
+## PR Rules
+
+- Every sample change must keep the sample compilable and runnable.
+- Sample changes must update the corresponding `README.md`.
+- Java and Scala variants of the same sample must stay in sync.
+- Dependency changes must verify Apache-compatible licenses.
+- Do not break the `docs-gen` build when changing samples referenced by documentation.
+
+## Formatting Rules
+
+- Prefer native scalafmt for changed Scala and SBT files when it is available.
+
+```shell
+git fetch origin main
+scalafmt --mode diff-ref=origin/main
+scalafmt --list --mode diff-ref=origin/main
+```
+
+- If native scalafmt is not installed, use the sbt scalafmt tasks or record that scalafmt could not be run.
+
+```shell
+sbt scalafmtAll scalafmtSbt
+sbt scalafmtCheckAll scalafmtSbtCheck
+```
+
+- Use JDK 17 for Java formatter tasks.
+
+```shell
+export JAVA_HOME=$(/usr/libexec/java_home -v 17)
+export PATH="$JAVA_HOME/bin:$PATH"
+sbt javafmtAll
+```
+
+- Run header generation before PR.
+
+```shell
+sbt headerCreateAll
+```
+
+- Do not rely on IDE formatting alone.
+- Do not commit unrelated formatting changes.
+
+## Validation Rules
+
+- Run the sample's tests.
+
+```shell
+cd pekko-sample-name
+sbt test
+```
+
+- Compile the sample to verify it remains valid.
+
+```shell
+cd pekko-sample-name
+sbt compile
+```
+
+- Run docs-gen to verify documentation generation.
+
+```shell
+cd docs-gen
+sbt run
+```
+
+- Always run `git diff --check`.
+- Do not assume local tools such as `sbt` or `scalafmt` are installed; if a required tool is missing, record the missing tool and skipped command in `Tests`.
+- Skipped or environment-failed commands must be recorded in `Tests`.
+
+## Code Rules
+
+- Samples must be self-contained and easy to understand.
+- Prefer clarity over cleverness in sample code.
+- Each sample should demonstrate a specific Pekko feature or pattern.
+- Keep Java and Scala variants functionally equivalent.
+- Use `scala.jdk.*` converters for Java/Scala interop in Scala samples.
+
+## Commit and PR Format
+
+- Use this body format for non-trivial commits.
+
+```text
+Motivation:
+Problem or requirement.
+
+Modification:
+Change summary.
+
+Result:
+New outcome.
+
+Tests:
+- command/result or Not run - docs only
+
+References:
+Fixes #1234, Refs #1234, or None - <short context>
+```
+
+- Use this PR body format.
+
+```markdown
+### Motivation
+Problem or requirement.
+
+### Modification
+Change summary.
+
+### Result
+New outcome.
+
+### Tests
+- command/result or Not run - docs only
+
+### References
+Fixes #1234, Refs #1234, or None - <short context>
+```
+
+- Never omit `Tests`.
+- Never omit `References`.
+- Use `Refs #...`, `Fixes #...`, or `None - <short context>`.
+- Do not add `Co-authored-by` or AI-assistant trailers to commits or PR descriptions.

CLAUDE.md

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+# Claude Rules for Apache Pekko Samples
+
+Follow `AGENTS.md`.
+
+Before opening or updating a PR, verify:
+
+- Changed samples compile and run successfully.
+- Java and Scala variants of the same sample stay in sync.
+- `README.md` is updated for any sample behavior changes.
+- Native `scalafmt` or the sbt scalafmt tasks were run for changed Scala/SBT files, or the missing tool is recorded in `Tests`.
+- `sbt javafmtAll` was run with JDK 17 when relevant.
+- `sbt headerCreateAll` was run to add headers for new files. Never hand-write or invent license headers; let sbt manage them, and preserve existing copyright notices intact.
+- `docs-gen` still builds correctly if samples referenced by documentation were changed.
+- Commit messages follow the `AGENTS.md` format.
+- PR bodies follow the `AGENTS.md` format.
+- `Tests` and `References` are present.
+- No `Co-authored-by` or AI-assistant trailers are added to commits or PR descriptions.