chore: update PR title convention and semantic types in AGENTS.md and CONTRIBUTING.md (#11620)

Since I and the agents sometimes get confused about which scopes and
types to use in our commits and PRs, I've created an explicit list that
we can verify against our existing `semantic.yml` file.

Co-authored-by: Marco A. <[email protected]>
Co-authored-by: Livio Spring <[email protected]>

.github/semantic.yml

@@ -1,2 +1,61 @@
 # Always validate the PR title, and ignore the commits
 titleOnly: true
+
+# Allowed types — the PR title type must be one of these.
+# This list is the single source of truth referenced by AGENTS.md and CONTRIBUTING.md.
+types:
+  - feat      # new feature
+  - fix       # bug fix
+  - docs      # documentation only (no code change)
+  - refactor  # code restructuring without behaviour change
+  - perf      # performance improvement
+  - test      # adding or fixing tests
+  - build     # build system or tooling
+  - ci        # CI/CD pipeline
+  - chore     # maintenance (deps, config, etc.)
+  - revert    # reverts a previous commit
+
+# Allowed scopes — if a scope is provided it must match one of these.
+# Scopes are optional; omit rather than invent one not on this list.
+# Note: 'docs' is a type, not a scope — use the type 'docs' for documentation changes.
+# This list is the single source of truth referenced by AGENTS.md and CONTRIBUTING.md.
+scopes:
+  # Backend — domain areas
+  - api
+  - session
+  - authz
+  - command
+  - query
+  - eventstore
+  - actions
+  - crypto
+  - domain
+  - feature
+  - idp
+  - notification
+  - oidc
+  - saml
+  - webauthn
+  # Backend — infrastructure
+  - cache
+  - config
+  - database
+  - migration
+  - setup
+  - telemetry
+  - queue
+  # Frontend
+  - console
+  - login
+  # API layer
+  - grpc
+  - proto
+  # Cross-cutting
+  - build
+  - ci
+  - deps
+  - i18n
+  - integration
+  - perf
+  - security
+  - test