fix(agent-core): honor abort signal in WebSearch and FetchURL tools

[Caldalis]

Related Issue

Resolve #1106

Problem

WebSearch and FetchURL ignored the per-call AbortSignal. Cancelling a turn
(Ctrl-C / turn abort) did not cancel an in-flight network request — it kept
running in the background, holding a connection, and on a slow or hung server it
lingered until undici's default timeouts.

Every other I/O-bound builtin tool (Bash, Grep, Agent, AskUser) already threads
ctx.signal into its work; the two web tools were the only exception, with no
comment explaining the omission, so this reads as an overs
intentional choice.

What changed

• Added an optional signal to the UrlFetcher and WebSearchProvider option objects.
• FetchURLTool / WebSearchTool now forward ctx.signal they destructured only toolCallId`).
• LocalFetchURLProvider, MoonshotFetchURLProvider, and MoonshotWebSearchProvider pass the signal to the underlying fetch(), which aborts both the header wait and the body read. The Moonshot → loc options object, so the signal flows through automatically.
• Tests: updated the call-shape assertions for the two tools and added provider tests asserting the signal reaches the underlying fetch.

This matches the existing cancellation pattern used by Bash/Grep/Agent and keeps the change focused. The touched interfaces (UrlFetcher /
WebSearchProvider) are internal to agent-core and are rface.

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update

[changeset-bot]

🦋 Changeset detected

Latest commit: 120345b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Patch

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[itxaiohanglover]

Clean threading of the abort signal through every layer — nice work. Tests covering both providers are solid. One small thing: MoonshotFetchURLProvider.fetch has a catch-all that swallows errors into empty content, so an abort there would surface as an 'empty content' error rather than a clean abort. Might be worth letting AbortError propagate, though it's a pre-existing pattern so no blocker.

[Caldalis]

Clean threading of the abort signal through every layer — nice work. Tests covering both providers are solid. One small thing: MoonshotFetchURLProvider.fetch has a catch-all that swallows errors into empty content, so an abort there would surface as an 'empty content' error rather than a clean abort. Might be worth letting AbortError propagate, though it's a pre-existing pattern so no blocker.

Thanks addressed in a follow-up: MoonshotFetchURLProvider.fetch now rethrows when the caller's signal is aborted, so a cancelled request surfaces as a clean abort instead of kicking off a fallback fetch. Genuine Moonshot failures (network errors) still fall back to the local fetcher as before. Added a test covering the abort doesn't fall back path.