refactor: remove callback thisArg support

[benlesh]

Summary

• remove thisArg overloads from every, filter, find, findIndex, map, and partition
• invoke callbacks directly and update tests to use closures or Function.prototype.bind
• classify the RxJS 7 receiver cases as intentional divergences and update migration and architecture documentation

Why

RxJS Next is not retaining the RxJS 7 thisArg convenience. Closures and bound functions provide the same behavior without requiring .call on every notification.

Validation

• 750 RxJS source tests
• affected cold/polyfill suites: 76/76 each
• exact complete audits: 2,299/39 cold and 2,316/22 polyfill, unchanged
• package build, public types, imports, migration freshness, installation audit, and lint
• packaged fallback/native Chrome kernel: 8/8
• performance: approximately 63.0M map values/sec and 140,627 cancellations/sec

[Copilot]

Pull request overview

Removes RxJS 7-style callback thisArg overloads from key RxJS Next Symbol APIs to simplify the public contract and eliminate per-notification .call overhead, while updating migrated/spec evidence and documentation to record the intentional divergence.

Changes:

• Removed thisArg overloads and .call(thisArg, …) dispatch from every, filter, find, findIndex, map, and static partition.
• Updated focused + ported tests and ported-manifest generation to use closures / Function.prototype.bind instead of receiver arguments.
• Updated migration and parity/compatibility documentation and evidence ledgers to classify the RxJS 7 receiver behavior as an intentional divergence.

Reviewed changes

Copilot reviewed 35 out of 35 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/rxjs/test/types/usage.ts	Adds type-level negative assertions rejecting thisArg arguments.
packages/rxjs/test/ported/tools/generate-port-manifest.mjs	Rewrites specific migrated programs to bind callbacks instead of using receiver args.
packages/rxjs/test/ported/platform/operators/map.spec.ts	Updates ported platform map tests to use bound/closure projectors.
packages/rxjs/test/ported/platform/operators/find.spec.ts	Updates ported platform find test to use predicate.bind(...).
packages/rxjs/test/ported/platform/operators/find-index.spec.ts	Updates ported platform findIndex test to use predicate.bind(...).
packages/rxjs/test/ported/platform/operators/filter.spec.ts	Updates ported platform filter tests to remove receiver usage.
packages/rxjs/test/ported/platform/observables/partition.spec.ts	Updates ported platform partition test to use bound predicate.
packages/rxjs/test/ported/migration-evidence-ledger.generated.json	Updates mappings/notes + classifications for receiver removal.
packages/rxjs/test/ported/manifest.generated.json	Reclassifies affected cases as intentional divergence and updates migrated programs.
packages/rxjs/test/ported/cold/operators/map.spec.ts	Updates ported cold map tests to use bound/closure projectors.
packages/rxjs/test/ported/cold/operators/find.spec.ts	Updates ported cold find test to use predicate.bind(...).
packages/rxjs/test/ported/cold/operators/find-index.spec.ts	Updates ported cold findIndex test to use predicate.bind(...).
packages/rxjs/test/ported/cold/operators/filter.spec.ts	Updates ported cold filter tests to remove receiver usage.
packages/rxjs/test/ported/cold/observables/partition.spec.ts	Updates ported cold partition test to use bound predicate.
packages/rxjs/test/ported/capability-registry.json	Updates capability mappings/notes to remove thisArg?.
packages/rxjs/test/kernel/contract.mjs	Updates kernel contract to validate map index behavior without thisArg.
packages/rxjs/src/partition.ts	Removes thisArg overloads and direct-invokes predicates.
packages/rxjs/src/partition.spec.ts	Updates focused partition spec to use closures instead of receivers.
packages/rxjs/src/map.ts	Removes thisArg overload and .call dispatch.
packages/rxjs/src/map.spec.ts	Removes focused spec that asserted RxJS 7 thisArg behavior.
packages/rxjs/src/find.ts	Removes thisArg overloads and .call dispatch.
packages/rxjs/src/find.spec.ts	Updates focused find spec to stop asserting receiver behavior.
packages/rxjs/src/find-index.ts	Removes thisArg overloads and .call dispatch.
packages/rxjs/src/find-index.spec.ts	Updates focused findIndex spec to stop asserting receiver behavior.
packages/rxjs/src/filter.ts	Removes thisArg overloads and .call dispatch.
packages/rxjs/src/filter.spec.ts	Updates focused filter spec to stop asserting receiver behavior.
packages/rxjs/src/every.ts	Removes thisArg overloads and .call dispatch.
packages/rxjs/src/every.spec.ts	Updates focused every spec to stop asserting receiver behavior.
packages/rxjs/MIGRATION.md	Documents removal of thisArg and recommends closures/bind (example needs a small fix).
packages/rxjs/docs/MIGRATION_EVIDENCE_LEDGER.md	Updates ledger table to include intentional-divergence classifications.
docs/rxjs-next/RxJS-7-parity.md	Updates parity mapping text to remove thisArg? from signatures.
docs/rxjs-next/PROJECT_PLAN.md	Records P6.11 completion evidence and session log entry.
docs/rxjs-next/OPEN_QUESTIONS.md	Updates overlap narrative to reflect thisArg removal decision.
docs/rxjs-next/DECISIONS.md	Adds D-059 and marks earlier thisArg-mentioning decision as superseded.
docs/rxjs-next/COMPATIBILITY.md	Updates overlap/compat narrative to remove thisArg and reference D-059.

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