docs(ai): Refresh AGENTS.md module list and fix coding.mdc command (#5517)

* docs(ai): Refresh AGENTS.md module list and fix coding.mdc command

The Module Architecture section omitted several product areas that now
exist as modules and already have dedicated .cursor/rules: Session
Replay, Feature Flags, Queues (Kafka), and JVM continuous profiling. Add
them alongside the other previously-unlisted modules, and add a pointer
to the repository's task-specific skills.

Also fix a typo in coding.mdc where the per-file test command used
./gradle instead of ./gradlew.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(ai): Note moving changelog entries to Unreleased on rebase

A rebase onto main can land a branch after a release was cut, leaving a
new changelog entry under an already-released version heading. Document
that the entry should be moved back into an Unreleased section at the
top of CHANGELOG.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(ai): Add changelog rebase note to AGENTS.md

AGENTS.md is the always-loaded entrypoint, so the rebase reminder reaches
agents more reliably here than in an on-demand .cursor rule. Keep the
detailed workflow in pr.mdc and point to it from here.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>