docs: clarify BIND9 9.20 branch strategy

docs/VERSION_SUPPORT.md

@@ -270,36 +270,20 @@ bind9-grammar/
 
 ## Version-Specific Features
 
-### Version Detection
+### Branch-Level Version Targeting
 
-The role will detect BIND9 version at runtime:
+The role currently uses branch-level version targeting instead of runtime version detection:
 
-```yaml
-# tasks/main.yml (planned implementation)
-- name: Detect BIND9 version
-  ansible.builtin.command: named -V
-  register: _bind9_version_output
-  changed_when: false
+- `main` targets BIND9 9.18.x LTS.
+- `9.20` targets BIND9 9.20+ feature releases.
 
-- name: Set BIND9 version facts
-  ansible.builtin.set_fact:
-    bind9_version_full: "{{ _bind9_version_output.stdout | regex_search('BIND (\\S+)', '\\1') | first }}"
-    bind9_version_major: "{{ _bind9_version_output.stdout | regex_search('BIND (\\d+)\\.(\\d+)', '\\1') | first }}"
-    bind9_version_minor: "{{ _bind9_version_output.stdout | regex_search('BIND (\\d+)\\.(\\d+)', '\\2') | first }}"
-```
+Each branch carries the templates, grammar data, documentation, and tests appropriate for its supported BIND9 series. This keeps generated configuration predictable and avoids mixing incompatible BIND9 grammar rules in one template path.
 
-### Conditional Configuration
+### Runtime Detection
 
-Templates will use version-aware conditionals:
+Runtime version detection is not part of the current implementation. The role does not set `bind9_version_full`, `bind9_version_major`, `bind9_version_minor`, or `bind9_version`, and templates do not branch on those values.
 
-```jinja2
-{# templates/named.conf.options.j2 (planned) #}
-{% if bind9_version_major | int >= 20 %}
-    {# BIND9 9.20+ specific options #}
-{% else %}
-    {# BIND9 9.18 options #}
-{% endif %}
-```
+Runtime detection may be reconsidered in the future if maintaining separate version branches becomes more expensive than supporting multiple BIND9 series from one branch. That future design would require dedicated tasks, public metadata, template changes, and Molecule coverage before being documented as supported behavior.
 
 ## Migration Guidance
 
@@ -367,4 +351,3 @@ See `CHANGELOG.md` for version-specific migration notes.
 | Date | Version | Changes |
 |------|---------|---------|
 | 2026-02-07 | 1.0 | Initial version support policy |
-