feat(ai): surface AI chat stream failures through one typed error channel (#22434)

## Context

Investigating a report where the AI chat showed only a `...` spinner
while the network response clearly contained `No AI models are
available`. Root cause: terminal stream failures reach the client on
**two mismatched channels**.

| Representation | Persisted (survives reload) | Rendered by client |
|---|---|---|
| AI-SDK `error` chunk (inside `stream-chunk`) | ✅ RPUSH'd to Redis | ❌
dropped by `readUIMessageStream` (no message part, no error state) |
| typed `stream-error` event | ❌ never persisted | ✅ sets the error atom
|

Live, the `stream-error` event renders. But on reload,
`chatStreamCatchupChunks` replays only the persisted **error chunk** —
which the reducer discards — and the streaming indicator never clears.

## Change

Collapse to a single typed error contract:

- **Suppress the opaque `error` chunk** in the stream job; every failure
is surfaced through the typed `stream-error` event. Errors are mapped
via `mapErrorToStreamError` so an `AiException` keeps its
`AiExceptionCode` (e.g. `API_KEY_NOT_CONFIGURED` → the existing "AI not
configured" banner) instead of leaking a raw string.
- **Persist the terminal error** next to the accumulated chunks and
expose it as an explicit `error { code message }` field on
`ChatStreamCatchupChunks`, so a client catching up after a reload
recovers it — no dependency on the AI SDK's internal chunk shape.
- **Reset per-thread stream state at job start**, so a failed turn's
leftover chunks/error never replay on the next stream.
- **Client replays the catchup error** as a terminal `stream-error`
event, which clears the streaming indicator and renders the error (fixes
the infinite spinner on a stream that ended in error).

## Notes

- `ChatStreamError` is a new metadata GraphQL type; generated types
(twenty-front metadata + client-sdk) were hand-updated to keep the tree
consistent and will be reconciled by CI's `graphql:generate` check if
anything differs.
- Server unit test added for the error mapping. No schema/DB migration.

## Test plan

- [ ] With no AI provider configured, send a chat message → error
renders immediately (not a spinner).
- [ ] Reload the thread → the error still renders (recovered from
catchup), indicator not spinning.
- [ ] Configure a provider and send again → normal streaming; no stale
error from the previous failed turn.


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packages/twenty-server/src/database/commands/upgrade-version-command/instance-commands.constant.ts

@@ -42,6 +42,7 @@ import { CreateApplicationTranslationCoreTableFastInstanceCommand } from 'src/da
 import { AddTsVectorFieldMetadataIdToSearchFieldMetadataFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-18/2-18-instance-command-fast-1810000001000-add-ts-vector-field-metadata-id-to-search-field-metadata';
 import { BackfillTsVectorFieldMetadataIdOnSearchFieldMetadataSlowInstanceCommand } from 'src/database/commands/upgrade-version-command/2-18/2-18-instance-command-slow-1810000003000-backfill-ts-vector-field-metadata-id-on-search-field-metadata';
 import { AddMetadataOverridesColumnFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-19/2-19-instance-command-fast-1820000100000-add-metadata-overrides-column';
+import { AddLastStreamErrorToAgentChatThreadFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-19/2-19-instance-command-fast-1821000000000-add-last-stream-error-to-agent-chat-thread';
 import { BackfillMetadataOverridesSlowInstanceCommand } from 'src/database/commands/upgrade-version-command/2-19/2-19-instance-command-slow-1820000110000-backfill-metadata-overrides';
 import { AddCacheTokensToAgentChatThreadFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-2/2-2-instance-command-fast-1777455269302-add-cache-tokens-to-agent-chat-thread';
 import { AddLogoToApplicationFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-2/2-2-instance-command-fast-1777539664664-add-logo-to-application';
@@ -175,5 +176,6 @@ export const INSTANCE_COMMANDS = [
   BackfillTsVectorFieldMetadataIdOnSearchFieldMetadataSlowInstanceCommand,
   AddMetadataOverridesColumnFastInstanceCommand,
   BackfillMetadataOverridesSlowInstanceCommand,
+  AddLastStreamErrorToAgentChatThreadFastInstanceCommand,
   DropMetadataStandardOverridesColumnFastInstanceCommand,
 ];