docs: document query cancellation semantics

[ColumbusLabs]

🎯 Changes

• document how to forward QueryFunctionContext.signal to abortable request clients
• clarify explicit collection cleanup versus on-demand subset unload cancellation behavior
• distinguish current behavior from the broader cancellation proposals in RFC RFC: Fixing the loadSubset / pagination core (no new features) #1657 and PR fix(query-db-collection): cancel idle on-demand queries #1573

Closes #350

✅ Checklist

• I have tested this code locally with pnpm test.

Additional verification:

• pnpm test:docs
• pnpm exec prettier --check docs/collections/query-collection.md
• pnpm lint
• pnpm test:sherif
• pnpm build
• pnpm --filter @tanstack/query-db-collection test

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

• Documentation
  • Added guidance for making collection requests cancellable using QueryFunctionContext.signal.
  • Documented how collection cleanup affects in-flight requests and when underlying requests are aborted.
  • Clarified the difference between eager cleanup and on-demand subset unloading, including cache reuse behavior.
  • Added references to planned cancellation and lease-policy improvements.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 1712cf6e-3225-4dce-8e7a-df799da03d71

📥 Commits

Reviewing files that changed from the base of the PR and between d70fb2a and 816df3e.

📒 Files selected for processing (1)

• docs/collections/query-collection.md

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📝 Walkthrough

Walkthrough

Adds documentation for forwarding QueryFunctionContext.signal to abortable request clients, cleanup-triggered cancellation, and on-demand subset unloading behavior.

Changes

Query cancellation documentation

Layer / File(s)	Summary
Signal cancellation semantics docs/collections/query-collection.md	Documents QueryFunctionContext.signal, collection.cleanup() cancellation behavior, client signal consumption requirements, subset unloading semantics, and related RFC/PR references.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Suggested reviewers: kyleamathews, kevin-dp

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the docs-only change about query cancellation semantics.
Description check	✅ Passed	The description follows the template and includes changes, checklist, and release impact sections.
Linked Issues check	✅ Passed	The docs cover all required issue #350 points, including signal usage, cleanup cancellation, subset unload behavior, and RFC/PR references.
Out of Scope Changes check	✅ Passed	The PR appears scoped to documentation only and adds no unrelated runtime or API changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[ColumbusLabs]

Closing in favor of #1694, which corrects the cancellation semantics and expands the documentation coverage. Thanks for carrying this forward.