fix(release-lines): synchronize the Classic 1.x descriptor on main

[zoeyrose]

Parent: #113

Outcome

Keep the main copy of the separately maintained Classic 1.x descriptor
synchronized with its authoritative release line without claiming Classic
runtime compatibility for replacement main.

Current drift

Both branches carry contracts/release-lines/classic-1x.json, and the file
identifies component: content-1x and branch: 1.x. The maintained 1.x
descriptor records compatible_classic_releases: >=5.10.1 <6.0.0, while
main's copy still says >=1.0.0 <2.0.0.

Main guidance references this file as the current descriptor of the separately
maintained Classic line; nothing marks it as a frozen historical snapshot.

Resolution

• Synchronize main's compatibility range to >=5.10.1 <6.0.0.
• Preserve component: content-1x, branch: 1.x,
  replacement_ready: false, and replacement_toolkit_package: false.
• Add validation that makes the descriptor's ownership explicit and prevents
  silent drift from the maintained 1.x value.

Release-line assessment

1.x is already authoritative and needs no authored change. This is a
main-only descriptor/test correction, not a declaration that main content can
run on Classic.

Acceptance criteria

• Both tips carry the same current Classic 1.x descriptor values.
• Main validation states that the contract describes content-1x, not
  main runtime compatibility.
• No authored content, gameplay, package, or generated artifact changes.
• python3 tools/validate.py and git diff --check pass on main.

[github-actions]

🎉 This issue has been resolved in version 2.3.3 🎉

The release is available on:

• v2.3.3
• GitHub release

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