W104 — Compatibility sweep: manifest, v0.10.0 baseline diff, real save loads

[The-Running-Dev]

Summary

Continues #447's partial W104 (the release-0.11 compatibility sweep), closing W104.1, W104.2, and W104.3.

• W104.1 — the sweep's manifest now also names every 0.10 built-in campaign and its recorded version (scripts/w104-manifest.test.ts), plus the new representative-save and v0.10.0-compat-baseline fixtures below, on top of the hosts/packed-consumer-surface coverage W104 (partial) — Release 0.11 Compatibility Sweep #447 already landed in regressionManifest.test.ts.
• W104.2 — fixtures/compat/v0.10.0/*.json freezes, per built-in campaign registry, the canonical initial Scene (projection + available actions + status) and Tier-1/2 validation findings, captured by running scripts/capture-compat-baseline.ts against the v0.10.0 tag in a throwaway worktree. capture-compat-baseline.test.ts reruns the identical capture at HEAD and diffs against the committed baseline — byte-identical across all five entries, since none of these built-in campaigns ever populated a field W93–W103 added (they predate the additive programme, so "0.11 additive fields omitted" holds by construction here rather than by a separate toggle).
• W104.3 — fixtures/saves/*.json are six real SaveEnvelopes (story-graph/simulation/world-graph × active/ended), produced by running committed replay fixtures through the real engine (capture-save-fixtures.ts). capture-save-fixtures.test.ts loads each through an actual SessionStore.loadGame (seeded via a test SaveRecordStore) and confirms the resulting scene matches an independent re-run of the same fixture's own action log — plus one negative case proving a tampered checksum is rejected with no partial write (no session ever created from the failed load).

W104.5 stays unmet. SubZeroDev.Adventures and the service-contract generator it names aren't present in this repository, so "client/host/Adventures/service-contract parity against one archive" can't be exercised from here — the same disposition #447 recorded for the criteria it deferred.

A judgment call worth flagging: no shipped campaign or kind has ever moved version between v0.10.0 and HEAD (20-contract.md already states this plainly). That means every W104.3 load takes the no-migration branch — genuine, but narrower than the criterion's name suggests. Migration logic itself is still only proven against the synthetic case in envelope.test.ts; there is nothing real to migrate from yet.

Test plan

• npm run typecheck — passes
• npm run lint — passes
• npm test — 1594 tests / 97 files, all passing (includes the new W104.1/.2/.3 suites)
• Manually verified both new comparison gates have teeth: tampered a compat-baseline field and a save's checksum, confirmed each test fails for the right reason, then reverted.