docs: document file naming conventions and clarify structure guidance

Added explicit file-naming rules to page-templates.md so agents know:
- Root entry-points: ALL-CAPS (AGENTS.md, README.md)
- Containers: <id>-<name>.md (e.g., 101-jellyfin.md)
- Infrastructure: lowercase-with-dashes (dns.md, auto-deploy.md)
- Plans/investigations: YYYY-MM-DD-slug.md
- Skills: lowercase-with-dashes/ folder containing SKILL.md

Updated AGENTS.md section 4 (Wiki conventions) to link to page-templates.md
and provided quick reference for file naming, page locations, and changelog format.

Updated README.md conventions section to mention file naming and link to
page-templates.md for the full rules.

All agents now have a clear reference chain:
  1. AGENTS.md (entry point) → points to conventions
  2. page-templates.md (structure) → has file naming + page templates
  3. writing-style.md (prose) → has voice, vocabulary, linking rules
  4. llm-wiki.md (organization) → has sources/wiki/index/log model

Verified: no broken links, all conventions documented, consistency check passes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -64,6 +64,7 @@ Resolved cases move to [`investigations/archive/`](knowledge/sources/investigati
 
 ## Conventions
 
+- **File naming.** Root entry-points are ALL-CAPS; containers use `<id>-<name>.md`; infrastructure pages use lowercase-with-dashes; plans and incident records use `YYYY-MM-DD-slug.md`. See [page-templates.md](.agents/shared/page-templates.md) for the full rules.
 - **Each node page** ends with a `## Changelog` section. Reverse-chronological. Entry format:
   ```
   ### YYYY-MM-DD — short title