docs: mark Sandboxwich snapshot historical

[haasonsaas]

Problem

The root notice identified Mono as authoritative, but contribution, documentation, and issue-intake surfaces still presented this repository as an active standalone source. That ambiguity allowed new source work to continue landing after publication authority moved.

Changes

• mark v0.1.17 as the final standalone release
• direct source changes and issue reports to evalops/mono/platform/execution/sandboxwich
• label the documentation map as a historical snapshot
• disable blank issue intake and link current reports to Mono

This does not archive, lock, delete, or change repository/package permissions.

Validation

• git diff --check — passed
• documentation-only change; no Rust/Postgres gates run

[haasonsaas]

Superseded by #412, which retained this PR’s historical/read-only messaging and exact publication-authority wording while also removing the remaining standalone workflow publication authority and adding executable guards. #412 merged as fae7a23; this draft must not be merged independently.