Automate Canton release note updates

[danielporterda]

Parent: #749

Current state

`docs-main/global-synchronizer/release-notes/canton.mdx` is copied manually from a Canton release-note file.

Goal

Automate updates for this published release-note page.

Scope

• Source: `canton:release-notes/*.md`, currently published from `release-notes/3.4.11.md`. Define the latest-stable selection rule as part of this task.
• Output: docs-main/global-synchronizer/release-notes/canton.mdx
• Route: /global-synchronizer/release-notes/canton

Acceptance criteria

• cf-docs has a repeatable command or workflow for refreshing this page.
• The process detects whether the upstream source changed before opening or updating a PR.
• The published route and page frontmatter are preserved.
• The PR body identifies the upstream source revision/version and summarizes changed release-note sections.