Add feature-flagged operation event adapter

[Sean Larkin (TheLarkInn)]

Part of #5978

Stack

Parent: #5992 (copilot/reporter-r3c-shadow-parity)

#5985 -> #5986 -> #5987 -> #5989 -> #5988 -> #5991 -> #5992 -> this PR

R6 #5993 remains a parallel fork from #5989 and is not included here. Keep auto-merge disabled while stack ancestors are open.

Architecture

• pass the frontend-owned reporter sink, session identity, and operation-stream opt-in to the selected Rush engine without exposing reporter instances or selection state
• adapt the existing phase-aware OperationGraph.eventSink and OperationExecutionRecord hooks into the existing OperationStreamEmitter; scheduling and operation identity remain project x phase
• emit registration (including silent metadata), previous/current status transitions, bounded ordered stdout/stderr chunks, authoritative stream close, and final operation outcome
• retain the existing parser-owned aggregate commandResult hook instead of emitting a competing result path
• bump the additive reporter protocol minor and update the beta API reviews/changefiles

Flag-off and presentation guarantee

When the reporter opt-in is disabled, the adapter does not expose a raw chunk callback, so OperationChunkTap is not installed. The existing StreamCollator, problem-matcher, stdout, and stderr pipeline remains byte-identical and authoritative.

When opted in, raw events flow to the manager, full-log file reporter, and explicit output sinks. The primary terminal reporter temporarily filters operation registration/status/output/close/completion events, so this slice cannot duplicate or suppress operation output while legacy collation still owns presentation.

Validation

• rush test --only @rushstack/rush-reporter --only @microsoft/rush-lib --only @microsoft/rush --verbose (6 operations; reporter 295 tests, rush-lib 766 tests, apps/rush 19 tests)
• rush build --to @rushstack/rush-reporter --to @microsoft/rush-lib --to @microsoft/rush --verbose (8 operations)
• rush check
• rush change --verify --no-fetch

Focused coverage includes event ordering, stdout/stderr separation, 64 KiB chunk boundaries, no duplicated/lost chunks, previous/current status and outcome mapping, phase-aware identity, repeated watch iteration identity, silent operations, no-sink behavior, disabled-tap behavior, and byte-identical flag-off output.

R5B non-goals

• no compact spinner/activity/result UI
• no plaintext/AI/legacy rendering parity ownership
• no full-log demo fixture or documentation
• no disabling of the legacy terminal destination
• no removal of StreamCollator or duplicate-output cutover

[Sean Larkin (TheLarkInn)]

Independent R5A review completed against #5978 and RFC phase 4.

Fixed in ac92280:

• collapsed sharded implementation records now feed one project x phase identity without losing shard output/failure state;
• raw stdout/stderr is tapped before newline normalization, including CR and unterminated chunks;
• cache-path terminal output now reaches the semantic stream;
• scheduling/pre-execution hook failures cannot leave registered operations without close/completion events.

Validation: focused OperationGraphEventSink suite (12/12), plus the inherited full reporter/rush-lib/apps-rush matrix on #5997 (304/773/28). No unresolved review threads. Auto-merge remains disabled because #5992 and earlier ancestors are open.

[Sean Larkin (TheLarkInn)]

Combined deep review of current head ac92280377.

1. HIGH operation stream close and completion are delayed until the entire graph ends. Per-operation consumers retain output and cannot finalize promptly. Emit from each record terminal path, with the graph-end loop only as a backstop.
2. MEDIUM protocol minor additions are marked required by default. Older same-major peers can accept the handshake and then discard the stream on an unknown event. Make new minor events optional through an explicit required set.
3. LOW OperationGraph.ts:679-680 duplicates executionRecords.set.

[Sean Larkin (TheLarkInn)]

Combined review findings fixed at 11a7f8462dd40b1d3c0d83ffafc5f0b748a80394.

• Operation close and completion now emit exactly once from each terminal record path, after final output and runner cleanup. The graph-end loop is an idempotent backstop for unfinished records.
• Protocol 1.1 operation terminal events are optional for 1.0 consumers. Unknown optional 1.1 events are skipped while the stream continues.
• The duplicate execution-record insertion was removed.
• Sharded mapping and aggregate status ownership remain inherited from Emit shadow Rush lifecycle events #5991 and are absent from the R5A delta.

Validation: reporter 298, rush-lib 782, apps/rush 47; focused operation tests 15; all three builds; API Extractor; rush check; stacked change verification. #5996 is CLEAN and auto-merge remains disabled pending fresh review.

[Sean Larkin (TheLarkInn)]

Final combined review of 11a7f8462d found no critical, high, medium, or useful low issues. Per-operation finalization, exactly-once terminal events, runner cleanup ordering, graph backstops, additive minor compatibility, feature-off behavior, cache, and watch paths are review-clean.