docs: add AGENTS.md and CLAUDE.md symlink (#2900)

Add agent-facing documentation covering monorepo structure, file-scoped
build/test/lint commands, testing conventions, and commit attribution
as required by the repository-docs standard.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: solnic

AGENTS.md

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+# Agent Instructions
+
+## Package Manager
+Use **Bundler**. Each gem has its own `Gemfile`; run commands from within the gem subdirectory.
+```bash
+cd sentry-ruby && bundle install
+```
+
+## Monorepo Structure
+| Gem | Path | Description |
+|-----|------|-------------|
+| `sentry-ruby` | `sentry-ruby/` | Core SDK — all other gems depend on this |
+| `sentry-rails` | `sentry-rails/` | Rails integration |
+| `sentry-sidekiq` | `sentry-sidekiq/` | Sidekiq integration |
+| `sentry-resque` | `sentry-resque/` | Resque integration |
+| `sentry-delayed_job` | `sentry-delayed_job/` | DelayedJob integration |
+| `sentry-opentelemetry` | `sentry-opentelemetry/` | OpenTelemetry integration |
+
+Shared test infrastructure lives in `lib/sentry/test/`. Root `Gemfile.dev` defines shared dev dependencies.
+
+## File-Scoped Commands
+Run from within the target gem directory (e.g. `cd sentry-ruby`):
+
+| Task | Command |
+|------|---------|
+| Install deps | `bundle install` |
+| Run all tests | `bundle exec rake` |
+| Run single spec | `bundle exec rspec spec/sentry/client_spec.rb` |
+| Lint | `bundle exec rubocop path/to/file.rb` |
+| Lint (autofix) | `bundle exec rubocop -a path/to/file.rb` |
+
+Root-level `bundle exec rubocop` lints the entire repo. Root-level `bundle exec rake` runs the E2E/integration spec suite (not individual gem tests).
+
+## Testing Conventions
+- Framework: **RSpec**
+- Spec files mirror source: `lib/sentry/client.rb` → `spec/sentry/client_spec.rb`
+- Isolated specs go in `spec/isolated/` (loaded in separate processes)
+- `sentry-rails` has `spec/versioned/` for Ruby-version-specific specs
+- Environment variables control version matrices: `RAILS_VERSION`, `SIDEKIQ_VERSION`, `RACK_VERSION`, `REDIS_RB_VERSION`
+- Every behavioral change needs a spec. Bug fixes need a regression test.
+
+## Commit Attribution
+AI commits MUST include:
+```
+Co-Authored-By: <agent-name> <noreply@example.com>
+```
+
+## Standards Overrides
+- Changelog: DO NOT update `CHANGELOG.md` as it is automatically generated during the release process
+- Linting: RuboCop with `rubocop-rails-omakase` base — see `.rubocop.yml`
+- See `CONTRIBUTING.md` for release process and contribution workflow

CLAUDE.md

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+AGENTS.md