fix(host): use session.snapshotEvents() for dsh-session >= 0.1.2-rc.1

[GImDX]

Problem

dsh-session 0.1.2-rc.1 removed the public events property on Session (replaced by snapshotEvents()). The /dsh-usage-chart/usage route still reads session.events, which is now undefined:

• foldRounds(undefined) throws TypeError: events is not iterable
• dsh-host-webserver wraps the uncaught handler error as a bare 400 empty response
• the client falls back to the empty observed-rounds path, so the per-round usage chart disappears for every loaded session

Verified against a live deployment on dsh-session 0.1.2-rc.1: /usage?session=<loaded session> returns an empty 400, /usage?session=<unknown> returns the plugin 404 JSON, and folding the same session log offline succeeds — the crash only occurs on the new runtime API shape.

Fix

• Prefer session.snapshotEvents() when present, with a legacy session.events fallback (?? [] so a missing API can never crash the route again)
• Align the vendored SessionEventLike type in types/cordis.d.ts (add required time, mark events optional, add snapshotEvents?)

Verification

• npm run typecheck clean
• node --test tests/*.test.mjs → 39/39 pass
• Replayed a real 13k-event session log through the patched fold path locally without errors

[Max-Samson]

@GImDX Thanks for the clean fix.
The feature detection (typeof session.snapshotEvents === 'function') and fallback to session.events ?? [] correctly handle the breaking change in dsh-session >= 0.1.2-rc.1 while preserving backwards compatibility.
I have added a dedicated unit test verifying both the snapshotEvents() preference and the fallback behavior under /usage. All 40 tests and typechecks pass.