ARN-66: port Foresight file-write prompt contracts

[rita-aga]

Summary

Ports the ARN-66 prompt/file-write fix onto GitHub main without taking over ARN-65's broader self-heal lane.

• adds red/green prompt contract tests across the six paw-foresight WASM prompt builders
• replaces ambiguous <file-id-from-temper.write> guidance with exact temper.write("/...md", ...) recipes and result["file_id"] capture instructions
• aligns agent manuals, including endpoint-writer BundleWritten wording for the diversity gate
• records topology and readiness proof in docs/proofs/2026-06-18-arn-66-foresight-port.md

Topology Notes

Verified canonical run target is the Railway foresight service on Supabase (aws-1-us-west-1.pooler.supabase.com), not the openpaw service on Railway Postgres. Both checked services remain configured for LLM_PROVIDER=openai_codex and LLM_MODEL=gpt-5.5; this PR does not change provider.

Genesis inspection found canonical temperpaw/paw-foresight@659e40c663024af1acf1ed6d2a39d872d3dbdf14 already contains Endpoint self-heal workflow markers (Sampled, ResumeWriter, state_timeout, UnderRepair), while GitHub main lacks those source commits. ARN-65 is the active owner for broader self-heal source convergence. This PR deliberately ports only the prompt/file-write contract delta.

DSF UI Note

Read-only inspection found the run-progress UI on local Deep Sci-Fi branch codex/dsf-2 (dfe5a904, efcc166f), not in the deployed April Railway backend. The UI path uses TEMPER_API_URL/TEMPER_API_KEY/TEMPER_TENANT and has no openpaw hardcode in the checked path, but a second DSF repo PR/deploy plus production Temper config is required before using it as canonical Foresight run proof.

Verification

cargo test --manifest-path os-apps/paw-foresight/wasm/sample_endpoints/Cargo.toml
cargo test --manifest-path os-apps/paw-foresight/wasm/seed_world/Cargo.toml
cargo test --manifest-path os-apps/paw-foresight/wasm/spawn_adversaries/Cargo.toml
cargo test --manifest-path os-apps/paw-foresight/wasm/spawn_repairers/Cargo.toml
cargo test --manifest-path os-apps/paw-foresight/wasm/render_artifacts/Cargo.toml
cargo test --manifest-path os-apps/paw-foresight/wasm/animate_dwellers/Cargo.toml
git diff --cached --check

See the proof doc for deployment evidence and the fresh-run readiness checklist.