[live1206]

Tracking microsoft#12454 (Task04). Stacked on feature/pre-emission-field-types and its upstream draft microsoft#12462.

Checkpoint

• Add bounded, generation-wide POC observations for ordinary type candidates, source currentness, and the approved header-finalization lifecycle; preserve native qualified fallback and independent Task03 decisions.
• Preplan POC declaration signatures and ordered parameter identities, and compare them with the values actually selected by the native writer. A failed sidecar cannot silently certify a later declaration it did not observe. On a declaration-selection rejection, detach that sidecar rather than repeating its failure bookkeeping; shared and independently funded observers remain separate.
• Not ready to merge: the POC remains non-authorizing (HasUncoveredEmission is true). This guard covers the reproduced parameter-selection schedule, not all ABA or whole-declaration omissions. Missing/unavailable native plans, other sidecar-failure paths, complete write-event and post-rejection resource accounting, ordinary authority, retention acceptance, the expanded current-source checkpoint, and a full independent review remain open.

Behavior validation

• The original standard-writer parameter-array ABA was rerun with the original debugger schedule: native output and the shared receipt remain unchanged, while the POC receipt and native-consumption check reject the observed substitution. Stable and persistent-mutation controls passed.
• Real Foo PipelineMessage planning, independent receipt/import budget and mismatch controls, and all 39 standard provider writes passed after the detachment change. A prior-sidecar-failure protocol control fails closed without invalidating the shared receipt or independent field decisions.
• A real 32/64-parameter debugger comparison confirmed native output and shared receipts unchanged while subsequent sidecar failure-bookkeeping calls fell from 33/65 to zero; the portable protocol control also passed.
• The 50-file/1,000-candidate source-work bound and 40-file documentation-capture bound continue to reject incomplete batches; local exhaustion remains isolated. The declaration-event ledger also has exact-limit and concurrent-reservation controls.
• A supported array and unsupported BCL read-only parameter carrier preserve the same native method output; the unsupported carrier does not produce the POC candidate in that fixture.