Default to using app-generated AbortSignal for wrapped fetch

[siosonel]

Description

Fixes https://gdc-ctds.atlassian.net/browse/SV-2774 and https://gdc-ctds.atlassian.net/browse/SV-2769.

dofetch3(), when called as a Vocab method, will now set an AbortSignal option if it's missing. Previously, chart data requests already supplied an AbortSignal option. This update supplies an AbortSignal even for non-chart data requests, such as for Correlation Plot variable inputs that query term-specific data, so that the app.dispatch() will not be triggered after such requests. Previously, the detection of stale non-chart data requests was centralized in app.dispatch(), but that assumed that app.dispatch() is triggered before the data request, which may not be true for non-reactive PP components like termsetting and requests like /termdb/descrstats that happen inside termsetting code.

Test:

• pull sjpp/master
• follow the steps in SV-2774
• there should be a cancelled /termdb/descstats request in the Network tab after switching to ALCHEMIST cohort and before the plot data request finishes for TARGET
• the rendered plot should have 1176 cases for ALCHEMIST and not re-render/change after waiting 30 seconds

Checklist

Check each task that has been performed or verified to be not applicable.

• Tests: Added and/or passed unit and integration tests, or N/A
• Todos: Commented or documented, or N/A
• Notable Changes: updated release.txt, prefixed a commit message with "fix:" or "feat:", added to an internal tracking document, or N/A
• Rust: Checked to see whether Rust needs to be re-compiled because of this PR, or N/A

[Copilot]

Pull request overview

This PR aims to reduce stale client-side termdb/vocab data requests by ensuring dofetch3() (when invoked as a Vocab/TermdbVocab method) defaults init.signal to an app-generated AbortSignal, so requests can be cancelled on app state changes (e.g. cohort switches).

Changes:

• Update client/common/dofetch.js:dofetch3() to default init.signal from this.app.getAbortSignal() when called as an object method and the caller didn’t provide a signal.
• Wire Vocab/TermdbVocab to call dofetch3 as an instance method (this.dofetch3(...)) to enable the above defaulting behavior.
• Add error-path cache cleanup to memFetch() and update related usage/docs/changelog.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
shared/utils/src/fetch-helpers.js	Adds rejection handling in memFetch() to clear cache entries on failed in-flight requests.
server/src/mds3.gdc.js	Removes passing q.__abortSignal into a cached /cases memFetch call.
client/termdb/Vocab.js	Exposes dofetch3 as an instance method for access to this.app.getAbortSignal().
client/termdb/TermdbVocab.js	Switches termdb API calls from dofetch3(...) to this.dofetch3(...).
client/common/dofetch.js	Adds defaulting of init.signal based on the caller’s this context; expands comments.
CHANGELOG.md	Documents the behavior change in dofetch3() for vocab usage.

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[Copilot]

@siosonel I've opened a new pull request, #4266, to work on those changes. Once the pull request is ready, I'll request review from you.