fix(tools): keep the forget-memory timeout when a caller passes a signal

[Agnik47]

Fixes #1549.

The problem

packages/tools/src/shared/forget-memory.ts combined the caller's signal and the 30s abort with ??, which makes them mutually exclusive:

signal: options?.signal ?? AbortSignal.timeout(FETCH_TIMEOUT_MS),

Pass a cancellation signal and the request becomes unbounded again — exactly the condition #1451 set out to remove. A caller who wants both cancellation and a timeout had no way to express it.

Latent rather than live today: neither production call site (ai-sdk.ts, openai/tools.ts) passes options. It becomes a real hang the first time someone wires up cancellation.

The fix

Compose the two signals instead of choosing between them:

signal: options?.signal
    ? AbortSignal.any([options.signal, AbortSignal.timeout(FETCH_TIMEOUT_MS)])
    : AbortSignal.timeout(FETCH_TIMEOUT_MS),

AbortSignal.any is available in Node 20.3+, Bun and workerd. Root package.json declares "node": ">=20", so in theory 20.0–20.2 are below the floor for this API; every maintained 20.x release is well past 20.3. Happy to guard it if you'd rather not rely on that.

Tests

The existing case — "uses a caller-provided signal instead of creating a timeout" — asserted the buggy behaviour (expect(init.signal).toBe(controller.signal)), so it could not survive the fix. It is replaced by two tests that pin the composed semantics:

• cancels through a caller-provided signal — the request signal is a composite rather than the caller's own, and aborting the caller still aborts the request.
• keeps the timeout when a caller-provided signal is present — AbortSignal.timeout is still called with 30_000, and firing only the timeout leg aborts the request.

Both new tests fail against the previous implementation (verified by reverting the source and keeping the tests):

× memoryForget > cancels through a caller-provided signal
  → expected AbortSignal { aborted: false } not to be AbortSignal { aborted: false }
× memoryForget > keeps the timeout when a caller-provided signal is present
  → expected "timeout" to be called with arguments: [ 30000 ]

Verification

• vitest run src/tool-operations.test.ts — 15/15 pass (was 14).
• Full packages/tools suite — 91 passed / 30 skipped. The two failing files (src/tools.test.ts, test/claude-memory.test.ts) fail identically on a clean origin/main checkout; they are the pre-existing collection errors tracked in @supermemory/tools fails check-types: 31 errors in test/, including an import of a file that no longer exists #1545, untouched by this change.
• biome check clean on both files; tsc --noEmit reports nothing on either file.

Unrelated, but noticed nearby

apps/mcp/src/server/client/index.ts:339 (getDocuments) has the identical options?.signal ?? AbortSignal.timeout(...) shape. Out of scope here — say the word and I'll open a separate issue or PR for it.