Add od-cfg-persist runbook + od-cfg-acl script

Persist Open Dental's 'Do not show this window on startup' by making
FreeDentalConfig.xml writable:
- Option A: one-time elevated save
- Option B (preferred): grant Users Modify via well-known SID S-1-5-32-545
- od-cfg-acl.ps1 auto-resolves 64/32-bit install path, iex-safe conventions
- Security note on reversible MySQL password in the config; limited user / Middle Tier
- Cites OD manual freedentalconfig.html / choosedatabase.html

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

README.md

@@ -66,7 +66,9 @@ run time — never commit filled-in values.
 | File | Purpose |
 |---|---|
 | [`od-smb-cred.md`](od-smb-cred.md) | Open Dental SMB share — stored-credential fix |
+| [`od-cfg-persist.md`](od-cfg-persist.md) | Open Dental — persist "Do not show this window on startup" (writable FreeDentalConfig.xml) |
 | [`scripts/cg-disable.ps1`](scripts/cg-disable.ps1) | Disable Credential Guard, then reboot (prompts to confirm) |
+| [`scripts/od-cfg-acl.ps1`](scripts/od-cfg-acl.ps1) | Grant Users Modify on FreeDentalConfig.xml (Option B of od-cfg-persist) |
 
 ## Tiers