Sync property write decline docs

[rogeralsing]

Summary

• remove stale retained-decline wording for nested named compound/logical writes now admitted by PRs Admit nested named compound writes #2975/Admit nested named logical writes #2976
• clarify computed expression-key assignment support from PR Admit computed expression-key writes #2977 without implying compound/logical/update neighbors route
• update durable rules so future slices keep retained-decline examples current

Verification

• rtk rg -n "deeper compound|box.child.value += …|box.child.value &&= …|box[key+suffix]|logical-assignment operators,\s*$|computed-expression keys)" docs/unified-bytecode-expansion-contract.md docs/rules/unified-bytecode-prototypes.md docs/rules/expression-bytecode-assignment.md (no matches)
• rtk git diff --check
• rtk dotnet test tests/Asynkron.JsEngine.Tests -c Release --filter "FullyQualifiedName~ExpressionProgramCoverageMapTests.UnifiedBytecodeExpansionContract_ListsRequiredHeadingsAndCurrentEnums" (1 passed; 7 unrelated existing nullable warnings in test files)

[Copilot]

Pull request overview

Updates unified-bytecode documentation to reflect recently widened support for nested named compound/logical property writes and direct computed expression-key assignments, and to remove now-stale “retained decline” examples so the contract/rules stay current with the production boundary.

Changes:

• Refreshes the production property-write boundary text in docs/unified-bytecode-expansion-contract.md (nested named compound/logical/update admission; computed-expression-key neighbors remain declined).
• Updates durable rule guidance in docs/rules/unified-bytecode-prototypes.md to reflect the expanded nested named receiver routing and computed expression-key assignment support.
• Tightens the “update boundary docs when admitting shapes” rule in docs/rules/expression-bytecode-assignment.md to discourage carrying forward stale decline examples.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
docs/unified-bytecode-expansion-contract.md	Removes stale retained-decline examples and clarifies current admission/decline boundaries for nested named writes and computed expression-key assignment.
docs/rules/unified-bytecode-prototypes.md	Updates the durable “nested named receiver writes” rule to reflect newly admitted shapes and clarify what remains declined.
docs/rules/expression-bytecode-assignment.md	Updates durable guidance to require boundary docs stay aligned with newly admitted property-write shapes and current declines.

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