aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace

Found by Codex review round 4 on PR #5236 (finding comment 4463375210), dispositioned there as a follow-up because it is an estimator redesign, not a defect fix in that PR's scope.

Problem. deriveEpicEta in pm-stack/aggregator/src/forecast.ts derives P50/P80 from the median / lower-quartile weekly pace. When the four complete primary weeks are [0, 0, 0, 4] closures and work remains, the local evidence floor passes (4 completions, 4 weeks) but the median weekly bucket is zero, so the result is no_measurable_pace with no dates despite positive measured throughput. Batch-delivery scopes (sufficient evidence, bursty weeks) get no forecast.

Contract. The forecasting design (doc/2026-11-01T21-07-00Z_design_pm-stack_forecasting/2026-11-01T21-07-00Z_design_pm-stack_forecasting.md §1, line 36) specifies: "Estimator: resample complete weekly completion buckets (including observed zero weeks) to estimate a distribution for remaining units / weekly throughput. Publish P50 and a conservative P80 completion range… If no weekly pace is measured, emit 'no measurable pace'". The current median/lower-quartile implementation is a simplification that does not implement the resampling estimator.

Acceptance criteria.

Deterministic (seeded) resampling over the complete weekly completion buckets, zero weeks included, estimating the distribution of weeks-to-complete for the remaining units; P50 and conservative P80 derived from that distribution.
[0, 0, 0, 4] with remaining work returns a forecast with finite P50 <= P80 instead of no_measurable_pace.
A truly zero total pace (all buckets zero) still returns no_measurable_pace with no dates.
Pinned tests updated with rationale where behavior changes (notably "zero lower-quartile pace: P50 present, P80 explicitly unmeasurable" in pm-stack/aggregator/test/forecast-3982.test.ts); new tests cover the bursty case and determinism (same input → same output).
Decide and record whether the estimator change bumps FORECAST_MODEL_VERSION (forecast/v1).
Full aggregator suite green (bun test in pm-stack/aggregator).

Links: PR #5236 · issue #3982 · queue task 8962

🤖 Agent note · handed off

Agent: queue worker (repo-worker-code), lane code-h
Session / ID: task 9471
Found via: queue claim
Task: Handed off to the opencode execution lane per §1b — the laptop claimant launches the bound opencode session for task 9471 (issue aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274).
Expectation: claimant session drives task 9471 to its terminal state under this queue's worker id
Links: n/a

🤖 Agent note · handed off

Agent: queue worker (repo-worker-code), lane code-l
Session / ID: task 9471
Found via: queue claim
Task: task 9471 (triage for issue aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274) is assigned to the opencode execution lane per repo-queue lane assignment; handing off to the laptop opencode claimant. Issue aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274 revalidated fresh this shift: OPEN, no hard-stop labels (held / user/owned / do-not-merge / do-not-auto-edit).
Expectation: claimant launches the bound opencode session and drives task 9471 to a terminal state: triage the resampling-estimator finding at current main, scope the fix path or close with evidence.
Links: issue aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274

🤖 Agent note · picked up

Agent: queue worker (repo-worker-code), lane code-f
Session / ID: task 9955
Found via: queue claim (resume)
Task: small_fix for issue aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274 — resuming from checkpoint stage awaiting_ci: PR aggregator(forecast): design §1 resampling estimator in deriveEpicEta (#5274) #6169 open (branch queue/9955-5274-resampling-estimator, commit c91fd5e), targeted tests passed on laptop per prior checkpoint. Codex gate check this shift: one P1 finding on PR aggregator(forecast): design §1 resampling estimator in deriveEpicEta (#5274) #6169 (generated model-backed coverage for the estimator, comment 4478278682) is undispositioned and blocks merge under the Codex findings gate — fixing it in the PR this shift.
Expectation: PBT/MBT coverage added with a named oracle, PR updated, then merge under standing criteria if verified
Links: issue aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274 · PR aggregator(forecast): design §1 resampling estimator in deriveEpicEta (#5274) #6169

test(forecast): generated model-backed coverage for the resampling es…

Merge pull request #6169 from developing-today/queue/9955-5274-resamp…

🤖 Agent note · done

Agent: queue worker (repo-worker-code), lane code-f
Session / ID: task 9955
Found via: queue claim (resume at awaiting_ci)
Task: PR aggregator(forecast): design §1 resampling estimator in deriveEpicEta (#5274) #6169 merged — merge commit f2a72d9; issue aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274 closed by the merge. This shift dispositioned the blocking Codex P1 (generated model-backed coverage): fixed in commit 2c2a5e9 with 240 generated cases against an exact DP reference oracle (explicit 2-week sampling tolerance; constant-bucket cases exact), replied on the Codex thread (discussion r4478517434). Tests: forecast-3982.test.ts 31 pass on laptop (bun test). Outcome: fixed_merged.
Expectation: none — terminal
Links: issue aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274 · PR aggregator(forecast): design §1 resampling estimator in deriveEpicEta (#5274) #6169

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aggregator(forecast): resampling estimator for epic ETA (design §1) — zero-median bursty buckets return no_measurable_pace #5274