feat(session): refuse session logs a build cannot faithfully read

Old runtimes meeting a newer session format now fail loud instead of
misreading: version refusal names the direction (newer: upgrade the
harness; older: no upgrade path) and points at the raw JSONL log, and an
event type outside the generated known vocabulary refuses resume unless
its envelope carries the new ignorable: true marker (default: required,
so a forgotten marker over-refuses instead of silently resuming a gutted
session). gen-persistence-catalog now also emits
KNOWN_SESSION_EVENT_TYPES; SQLite stores the marker in a dedicated
column (SCHEMA_VERSION 15). The versioning design (monotonic integer,
n->n+1 upgrader chain, migrate-on-continue) is recorded in the
session-log-version-mechanism Agent Note.

AGENTS.md

@@ -100,7 +100,7 @@ Real-API tests and demos read `DEEPSEEK_API_KEY`, optional `DEEPSEEK_BASE_URL`,
 - ESM everywhere (`"type": "module"`). Use package names across packages and `.ts` in local relative imports. Config subprocesses run built `lib/` under plain Node; source regressions use their declared launcher ([testing policy](docs/testing.md#test-subprocess-launch-modes)). The `dsh` CLI source launch runs through tsx's ESM-only hook (`node --import tsx/esm`); modules it reaches must stay ESM (no CJS-only exports) — Node's native TypeScript modes are unavailable across the engines range ([source-launch contract](.agents/notes/implemented/architecture/2026-07-29-dsh-source-launch-tsx-esm.md)). Raw/Web `cordis.yml` bare plugins must appear in their resolver manifest's `dependencies`; `verify-cordis-config` enforces it.
 - **Registrations are effects**: every contribution goes through `ctx.effect()` / `ctx.on()`; a registry's `register()` returns the disposer.
 - **Runtime invariants assert owned relationships.** Check authoritative event streams or mutable data, not service or method presence, plugin metadata or effects, or fixed pure examples. Without a plausible relationship, an explained empty companion is correct ([package invariant rules](packages/AGENTS.md)).
-- **Typed events use declaration merging** and merge-extensible maps. Event JSDoc needs `@mode` and payload `@param`; scoped keys absent from payloads need `@dshScopeScan unsupported`. Public service methods document parameters and non-void returns.
+- **Typed events use declaration merging** and merge-extensible maps. Event JSDoc needs `@mode` and payload `@param`; scoped keys absent from payloads need `@dshScopeScan unsupported`. Public service methods document parameters and non-void returns. A `SessionEventMap` member is required-on-read by default — builds that do not know its type refuse the log unless the event carries the envelope's `ignorable: true`; only structural format changes bump `SESSION_FORMAT_VERSION` ([mechanism](.agents/notes/implemented/architecture/2026-08-10-session-log-version-mechanism.md)).
 - **Switch on discriminant tags.** Closed unions end in `assertNever`; merge-extensible unions fall through a documented default.
 - **Waterfall listeners MUST call `next()`** to delegate; returning without it short-circuits the chain ([semantics](docs/cordis-primer.md#cordis-waterfall-semantics)).
 - **Model-visible ⟺ logged**: anything that reaches a model request must be reconstructable from the session log; a new model-visible input requires a session event.