Document MySQL branch copy behaviour and TLS steal scoping

[skreborn]

Resolves INT-747.

Documents what a MySQL or MariaDB branch copy carries and the server settings it mirrors, the grant needed to copy routines defined by other accounts, the new serverName field on TLS steal configs, and that a steal config without targetPath or selector applies to every target in its namespace.

[linear-code]

INT-747

[greptile-apps]

The PR appears safe to merge, with a non-blocking documentation gap around the minimum versions required for serverName.

Findings

1.  Minimum versions remain unspecified ▶

Fix with agent prompt

### Issue 1
docs/using-mirrord/incoming-traffic/steal-https.md:26
The compatibility note introduces the version-gated `serverName` field without naming the minimum operator and agent versions that support it. Directing users to an unidentified release's changelogs prevents them from determining whether their installation accepts the example configuration.

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For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

Summary

This PR documents MySQL and MariaDB branch-copy behavior and adds guidance for scoping TLS steal resources and configuring TLS server-name verification.

• Explains which database objects and server settings branch copies preserve.
• Documents privileges needed to copy routines owned by other database accounts.
• Warns about unscoped TLS steal configurations and adds agentAsClient.verification.serverName.
• The new version-gated TLS field lacks concrete minimum supported versions.

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