feat(datetime): complete php-src 8.5 date compliance

[Guikingone]

Supersedes #632 and #821.

Status

Work in progress; this draft is an incremental checkpoint, not a claim of exhaustive php-src compliance. Final GPT-6 Astra review (low), the complete PHPT campaign and final target acceptance remain pending.

Checkpoint: 2026-09-08

• Rebased on origin/main at 640380cf8856379228db77e48c142d7613ed4e48, preserving upstream signature, PCNTL, Closure and diagnostic changes alongside the DateTime work.
• Latest checkpoint: d07ae8bc7dbe1af46bd5c64095b5723f0281facf.
• Calendar/ISO/timezone procedural mutations now use native receiver dispatch. Timelib formatting and DateTime offsets use explicit timezone data instead of temporarily changing the request default.
• The post-eval retention scan no longer triggers user debug projections; variable/cell property references acquire a read owner. Other alias/container traversal remains under audit.
• Fixed the internal pointer-to-string alias's ownership contract; the calendar mutation regression now has no unexpected notices and a clean heap.
• DateTime procedural time mutation now bypasses subclass overrides through AST/EIR native dispatch, preserves receiver identity, binds named/default arguments and rejects immutable receivers.
• Fixed native/eval argument, default-value and result ownership uncovered by the date tests. Repeated time mutation and subsequent formatting pass the strict clean-heap regression.
• Added catchable ParseError/CompileError support, compile-warning replay, native DateTime debug projection and associated regression coverage. Remaining diagnostic/reflection limitations are explicitly tracked.
• Regenerated builtin/symbol documentation and the PHP compatibility page from the merged catalog.

Validation on this checkpoint

After the latest rebase: warning-free exporter build, clean native calendar-mutation heap regression, regenerated docs, site audit and EIR boundary audit all pass. The additional focused results below were obtained before this latest synchronization; exhaustive current-revision acceptance remains pending.

• Focused lexer, context/PCNTL, native-dispatch and builtin-contract unit tests pass.
• Three native date_time_set regressions pass, including strict heap cleanup; the mixed string-result/property preservation regression passes.
• The native/eval bridge assembly fixture emits for macOS AArch64, Linux AArch64, Linux x86_64, iOS device and iOS Simulator. This is emission evidence, not executable coverage of every target.
• Exporter build is warning-free; builtin documentation audit, generated-site validation, EIR boundary audit and staged diff hygiene pass.

Still open

• Remaining procedural DateTime/DateInterval/DateTimeZone parity cases, complete diagnostics and exception trace metadata, and residual ownership/coercion paths.
• Dynamic ReflectionClass construction in AOT and eval trace access; omitted initial value for AOT array_reduce. Their pending regressions remain enabled rather than ignored.
• Exhaustive php-src PHPT and target validation, final Astra audit/corrections, and final commit squash.

See .plans/datetime-astra-post-rebase-remediation.md for the detailed findings and evidence. The draft must not be treated as ready to merge while these gates remain open.