- Remove T & Tool<any,any,any> intersection in DistributedToolCallEnd
  that caused tsc to resolve input as unknown for all tools
- Relax SafeToolInput constraint to structural match (no generic bound)
- Fix "Zod schema inference" → "Standard Schema inference" in JSDoc/docs
- Fix off-by-one line number in StreamChunk.md reference
- Fix misleading test comment about searchClientTool
- Add | undefined to input type annotation in streaming docs
- Broaden server-tools.md tip to cover all typed tool variants
- Add tests for mixed Zod+JSON Schema and chat() with server/client tools

…xploring-wall

# Conflicts:
#	docs/reference/type-aliases/StreamChunk.md
#	packages/typescript/ai/src/activities/chat/index.ts
#	packages/typescript/ai/src/types.ts

Main's upstream bump to `@ag-ui/core` switched the AG-UI event interfaces
to `z.infer<...>` of a `"passthrough"` `z.ZodObject`, which introduces an
`[k: string]: unknown` index signature. `ToolCallStartEvent<TToolName>` was
declared as `Omit<AGUIToolCallStartEvent, 'toolCallName'> & { toolCallName: TToolName; ... }`
— and `Omit` on an index-signature'd type collapses the re-declared field
in ways that destroy discriminated-union narrowing on `StreamChunk`.

Consequences before this change:
  - `Extract<StreamChunk, { type: 'TOOL_CALL_START' }>['toolName']` resolved
    to `never`, so every type-check test around `TypedStreamChunk` failed.
  - `switch (chunk.type) { case 'TOOL_CALL_START': ... }` in `chat/index.ts`
    and `handleToolCallStartEvent`'s `Extract<..., {type:'TOOL_CALL_START'}>`
    parameter couldn't narrow, cascading 60 tsc errors through
    `activities/chat/**`, `middlewares/content-guard.ts`, and tests.

Redesign (types.ts):
  - `ToolCallStartEvent<TToolName>` now `extends AGUIToolCallStartEvent`
    with **no `Omit`**. The AG-UI `toolCallName: string` is inherited
    verbatim on the base interface; narrowing to a literal happens purely
    through intersection in the per-tool variants.
  - `ToolCallEndEvent<TToolName, TInput>` extends cleanly the same way.
    `toolName` is kept required (matches pre-merge TanStack surface and
    every adapter emits it).
  - `HasTypedTools<TTools>` now partitions out `ProviderTool` before
    checking `string extends ... ['name']`. Provider tools carry opaque
    provider metadata with a generic `string` name — without filtering,
    a user passing `[webSearchTool, myTypedTool]` would silently fall
    through to the untyped branch.
  - `DistributedToolCallStart` / `DistributedToolCallEnd` now distribute
    over `NonProviderTools<TTools>` and match any tool-like shape via
    `T extends { name: infer TName extends string }` — picking up
    `Tool`, `ServerTool`, and `ClientTool` uniformly.
  - The `ProviderTool` partition uses a structural brand match
    (`{ readonly '~provider': string; readonly '~toolKind': string }`)
    to avoid a circular import between `types.ts` and `./tools/provider-tool.ts`.

Test fix (tests/tool-calls-null-input.test.ts):
  - Two fixture calls to `manager.completeToolCall(...)` now include
    `toolCallName` / `toolName`. The runtime type requires them; the
    pre-merge test relied on the optional-ness accidentally introduced
    by the Omit-based surface.

Minor bucket from the review:
  - docs/chat/streaming.md: replace the hallucinated `gpt-5.2` model id
    with `gpt-4o` in all four occurrences (lines 27, 49, 109, 134).
  - examples/ts-react-chat/src/routes/api.tanchat.ts: remove the dead
    `typedStreamShowcase` function (`void typedStreamShowcase`).
  - packages/typescript/ai-svelte/src/create-chat.svelte.ts: wrap
    `onResponse`, `onChunk`, and `onCustomEvent` the same way
    `onFinish`/`onError` already were, so callers can mutate the
    `options` object and propagate new callbacks (matches the
    React/Preact/Vue/Solid sibling wrappers). Comment explains why.
  - Add `.changeset/svelte-callback-propagation.md` (patch bump).

Verification:
  - `pnpm --filter @tanstack/ai test:types` emits zero errors.
  - `pnpm --filter @tanstack/ai test:lib`         735/735 passing.
  - `pnpm --filter @tanstack/ai-openai test:lib`  131/131 passing.
  - `pnpm --filter @tanstack/ai-anthropic test:lib` 62/62 passing.
  - `pnpm --filter @tanstack/ai-svelte test:lib`   53/53 passing.
  - `pnpm --filter ... test:types` green across the same four packages.

Bucket (a) fixes from a 7-agent unbiased review:

1. ai-svelte createChat: restore awaitable onResponse contract
   - Was: `void options.onResponse?.(response)` discarded the Promise
   - Now: `(response) => options.onResponse?.(response)` returns it
   - ChatClient awaits onResponse() (chat-client.ts:611) — voiding broke
     the await and let async user work race with stream cleanup. Matches
     Vue/Solid/Preact pattern; the void was a lint-silencer mistake
     introduced during the main-merge resolution.
   - Call sites: 1 (the wrapper itself, rewritten). The wrapper's callee
     contract is `(response?: Response) => void | Promise<void>` —
     returning the Promise still satisfies it.

2. docs: split TypedStreamChunk into its own reference page
   - StreamChunk.md previously held two `# Type Alias:` H1s under a single
     id/title, breaking the per-alias-file convention and leaving the
     TypedStreamChunk type signature truncated (no `= ...` body).
   - New TypedStreamChunk.md includes the full conditional-type body and
     replaces the invalid `inputSchema: /* Zod schema */` placeholder with
     real Zod expressions.
   - StreamChunk.md trimmed back to one alias plus a cross-link.

3. type-check tests: guard NonProviderTools partitioning
   - Added a `fakeProviderTool` fixture and two regression tests:
     - ProviderTool-only arrays fall back to untyped events
     - Mixed [ProviderTool, typed tool] arrays still narrow the typed tool
   - Without these, a regression in HasTypedTools that fails to strip
     ProviderTool would silently widen toolName back to string.

Verification:
- pnpm --filter @tanstack/ai test:types: green
- pnpm --filter @tanstack/ai-svelte test:types: green
- pnpm --filter @tanstack/ai test:lib: 940 passed (+2 new)
- pnpm --filter @tanstack/ai-svelte test:eslint: 0 errors

The new TypedStreamChunk reference page introduced in 2b0bd96 links
to ./TaggedCustomEvent, but the corresponding page didn't exist yet —
CI's verify-links script flagged it as broken. Materialize the page
manually (TypeDoc would generate it on the next docs regen) so the
cross-link resolves and consumers landing on TypedStreamChunk can
follow through to the tagged-CUSTOM-event union description.

The page documents the four tagged variants (structured-output.*,
approval-requested, tool-input-available), the T parameterization on
StructuredOutputCompleteEvent, and the user-emitted-event caveat that
keeps the bare CustomEvent out of the union to avoid value: any
poisoning.

Verification:
- node scripts/verify-links.ts: green (0 broken links across 299 files)

Call-site enumeration:
- TypedStreamChunk.md:33 — './TaggedCustomEvent' link now resolves.
- StreamChunk.md, no link to TaggedCustomEvent (unchanged).
- No other files reference the page.

Round-2 CR confirmation flagged that the JSDoc claimed 'tagged custom
events still narrow' in the no-typed-tools branch, but the implementation
falls back to plain StreamChunk (no TaggedCustomEvent union) for
back-compat with AsyncIterable<StreamChunk> consumers. Consumers reading
the JSDoc would write code assuming tagged narrowing on bare chat() calls
and find runtime CustomEvent shapes that don't match the type-narrowed
expectation.

Rewrite the fallback paragraph to state the actual behavior: plain
StreamChunk fallback, opt into typed tools to get TaggedCustomEvent
narrowing alongside per-tool TOOL_CALL_*.

Call-site enumeration:
- types.ts:1571 TypedStreamChunk — JSDoc only, no signature change.
- Implementation at 1576-1587 is unchanged; verify-types green.
- docs/reference/type-aliases/TypedStreamChunk.md already accurately
  describes the fallback (line 31 'falls back to plain StreamChunk') so
  the reference doc and source-of-truth comment are now consistent.

Verification:
- pnpm --filter @tanstack/ai test:types: green
- node scripts/verify-links.ts: 0 broken links

Round-3 CR confirmation flagged that the streaming-structured branch of
chat() cast its return to TextActivityResult<TSchema, TStream> while the
other three branches use TextActivityResult<TSchema, TStream, TTools>.
The cast is type-equivalent today (the structured-stream branch of
TextActivityResult doesn't reference TTools) but the visual asymmetry
is a future-rot hazard — a later refactor that does parameterize the
structured branch on TTools would silently miss this site.

Call-site enumeration:
- chat/index.ts:2161 — the cast itself, updated.
- No other call sites cast to TextActivityResult; all consumers receive
  the return value from chat()'s narrowed conditional type.

Verification:
- pnpm --filter @tanstack/ai test:types: green
- node scripts/verify-links.ts: 0 broken links