feat(planning): complete verified explanations and trace delivery (#46)

Implement plan explanations, original decision traces, calendar replay, and worker counterfactual analysis. Preserve incomplete checkpoints and conflict reasons, with accessible navigation and localized comparison details.

Keep planning outcomes independent of tracing and bound worker delivery with receiver acknowledgements. Retain complete candidate history while releasing temporary buffers and benchmark references.

Validated with 201 tests, app/spec type checks, lint, production build, baseline outcome comparisons, and repeated loaded browser measurements. Document performance and remaining limits.

docs/benchmark/README.md

@@ -5,7 +5,9 @@ Open the deployed application at `/benchmark` on the reference phone. Tap
 report** and save the tab-separated output with the date and build identifier.
 
 The harness measures preparation, planning-to-outcome latency, later trace
-delivery, and total wall time separately. It records the outcome, last
+delivery, and total wall time separately. It also reports planning work, trace
+capture, trace materialization, and trace transfer independently, plus the
+largest extra delay of a 50 ms UI heartbeat. It records the outcome, last
 completed quality stage, placement count, determinism, trace status, and trace
 candidate count. `PlanningIncomplete` is not a conflict: its last completed
 stage and incumbent are retained.
@@ -30,9 +32,18 @@ stage and incumbent are retained.
 
 The browser page uses the same `createPlanningCalculation(request)` context as
 the calendar and adds no solver or backend dependency. The ten-second release
-ceiling applies to planning latency; trace delivery is reported separately and
+ceiling applies to planning work; trace delivery is reported separately and
 cannot replace a valid planning outcome.
 
+`planning_ms` is the observed latency until the outcome is usable;
+`planning_work_ms` excludes trace capture. `trace_capture_ms` accounts for
+instrumentation during planning, `trace_materialization_ms` accounts for
+building the stable explanation and finishing the trace after the outcome.
+`trace_transfer_ms` measures worker transfer and receiver assembly work;
+`trace_delivery_ms` measures elapsed time until the complete trace is ready. `max_ui_delay_ms` includes
+planning, trace delivery, and report preparation. Trace readiness has no
+ten-second ceiling and never permits truncating actual candidate evaluations.
+
 ## Hardware status
 
 No reference-phone run has been recorded. The project owner elected to close
@@ -72,3 +83,68 @@ loaded year	1	0.3	5901.5	5677.7	11581.0	Plan	dates	144	baseline	ready	865117
 loaded year	2	0.8	6167.5	7582.4	13752.4	Plan	dates	144	yes	ready	865117
 loaded year	3	0.6	5738.3	6219.5	11962.5	Plan	dates	144	yes	ready	865117
 ```
+
+## Exact-trace verification — 2026-10-03
+
+Working changes based on `0ce33cc9d6fe7381965a9162571abe205d0b7350`,
+Chromium 149.0.7827.55 on the same AMD Ryzen 7 7800X3D desktop,
+412×915 pixels, device scale 2.625, touch enabled, and 4× CPU throttling.
+One warm-up preceded three recorded repetitions. This is desktop emulation;
+no physical-phone result is claimed, and the earlier release exception is not
+used as evidence for this implementation.
+
+All five scenarios matched their pre-change outcomes in a separate core
+comparison, including traced versus untraced runs. Every repeated browser
+outcome matched its first repetition. Each loaded run returned 144 placements
+and retained all 868,919 actual trace candidate records with a ready trace.
+
+Loaded planning work took 5.81–6.18 seconds, below its ten-second budget.
+Observed outcome latency was 10.36–10.85 seconds, including trace capture;
+this latency is distinct from the planning-work budget. Complete trace delivery
+followed 24.09–25.10 seconds later. No evaluation was truncated to meet a timing
+target. The worst extra delay of the 50 ms heartbeat was 946.8 ms across the
+loaded runs, including report preparation, compared with 4.65–5.49 seconds
+before acknowledged delivery in the same final-trace harness.
+
+The worker stages snapshots during planning and delivers at most sixteen
+64-operation packets before waiting for receiver acknowledgements. The
+receiver applies bounded batches, releases consumed packets, and yields
+between tasks. The worker stops after its terminal packet; benchmark helpers
+keep completed trace references out of the next repetition. These changes
+avoid the observed message-flood pauses and repeated-run renderer crashes.
+The complete trace still requires substantial memory: a separate unthrottled
+core profile retained approximately 1.06 GB of heap for the loaded trace.
+These results do not establish physical-device performance.
+
+A separate rendered-calendar run at the same emulated mobile size used twelve
+balances of twelve days each. It produced 144 placements, 113 gained
+non-working days, and a longest work sequence of five. Full trace navigation
+and date comparison completed without browser errors. Maximum extra heartbeat
+delays were 487.4 ms during planning and calendar rendering, 380.8 ms during
+trace exploration, and 540.3 ms during comparison. Keyboard navigation,
+dialog focus restoration, background comparison without an implicit modal,
+and responsive widths of 375, 768, and 1440 pixels also passed.
+
+The final suite passes 201 tests across 23 files, application and specification
+type checks, ESLint, and the production build. Build warnings remain for the
+2.55 MB initial bundle (2.50 MB warning budget) and 13.41 kB calendar stylesheet
+(8.00 kB warning budget); hard budgets are not exceeded.
+
+```tsv
+scenario	repetition	preparation_ms	planning_ms	trace_delivery_ms	wall_ms	outcome	last_stage	placements	deterministic	trace_status	trace_candidates	max_ui_delay_ms	planning_work_ms	trace_capture_ms	trace_materialization_ms	trace_transfer_ms
+representative year	1	0.0	622.4	716.9	1340.3	Plan	dates	30	baseline	ready	29296	18.2	265.0	256.4	7.4	166.4
+representative year	2	0.0	593.5	695.8	1289.4	Plan	dates	30	yes	ready	29296	14.5	255.3	233.8	7.5	184.1
+representative year	3	0.0	592.0	721.0	1313.2	Plan	dates	30	yes	ready	29296	11.5	256.1	234.4	9.2	191.8
+typed obligations	1	0.1	259.7	324.3	584.6	Plan	dates	10	baseline	ready	13005	11.8	106.8	56.6	3.7	70.2
+typed obligations	2	0.1	266.2	330.6	596.9	Plan	dates	10	yes	ready	13005	11.7	110.6	60.3	4.1	81.9
+typed obligations	3	0.1	259.6	341.8	601.5	Plan	dates	10	yes	ready	13005	15.7	112.3	54.7	4.0	75.9
+chained earned entitlements	1	0.1	94.5	3.0	97.6	Plan	dates	3	baseline	ready	15	0.8	3.4	1.3	0.9	0.3
+chained earned entitlements	2	0.0	100.2	2.5	102.7	Plan	dates	3	yes	ready	15	0.2	3.6	1.4	0.7	0.1
+chained earned entitlements	3	0.0	96.0	1.5	97.5	Plan	dates	3	yes	ready	15	0.1	3.2	1.5	0.7	0.1
+deliberate conflict	1	0.0	94.4	2.4	96.8	PlanningConflict		0	baseline	ready	4	0.2	0.9	0.8	0.3	0.2
+deliberate conflict	2	0.0	93.2	1.0	95.0	PlanningConflict		0	yes	ready	4	0.2	1.1	0.5	0.2	0.0
+deliberate conflict	3	0.1	92.8	1.6	95.2	PlanningConflict		0	yes	ready	4	1.4	1.0	0.7	0.2	0.1
+loaded year	1	0.0	10852.1	25102.6	36002.9	Plan	dates	144	baseline	ready	868919	946.8	6014.8	4730.6	948.3	8862.1
+loaded year	2	0.1	10364.4	24816.9	35216.6	Plan	dates	144	yes	ready	868919	791.2	5813.1	4440.6	296.7	8693.3
+loaded year	3	0.1	10807.8	24089.4	34933.6	Plan	dates	144	yes	ready	868919	721.7	6176.0	4526.6	978.7	8408.0
+```