docs(agents): plan W3 deterministic test support

[blakinio]

Purpose

Accept one bounded W3 launch plan for deterministic Rust test support and fake-time helpers after the completed W2 wave.

Live state

• base main: 0b1cd7914c04efd6b41a4a1b975234df715e6104
• W1/W2 completed and archived
• open PRs feat(ui): prototype Oteryn login shell #23/fix(assets): select release archives by client version #37 are legacy-only; ci: prove official Tibia login without OCR on Synology #48 is isolated operational work
• no active Rust task or PR owns test support, Cargo/lockfile integration or the proposed public surface

Delivered plan

• exactly one implementation worker W3-TEST;
• one unique Cargo/lockfile/shared-document lease;
• worker prompt NEXT_TEST_SUPPORT_AGENT.md;
• package consumes oteryn-foundation::ManualClock and oteryn-diagnostics;
• category tool, so architecture checker/fixtures remain read-only;
• W1/W2 relaunch remains prohibited.

Boundaries

No package implementation in this coordination PR. No async runtime, executor, scheduler, global registry, product service, protocol, assets, UI or external-repository changes.

Task

OTC-20260729-plan-w3-test-support

Validation

Exact final head: 164c8d0b5fb74c8dd433389fbaa84fde07fa9e01.

• live overlap/base review passed;
• complete five-file path/content/full-diff review passed;
• Rust Client run 30431875004 passed Windows workspace and Supply Chain;
• repository CI run 30431875234 passed all required jobs and CI / Required;
• final exact-head rerun is required before readiness/merge.