Rename eval/ decision log to simulations/; bump pumpingStation pointer

Follows pumpingStation@3e13512 (rename eval/ → simulations/). The
decision log file is renamed to match the new folder name; an
addendum in the body explains that the rename was a naming
clarification, not a rationale change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.agents/decisions/DECISION-20260422-pumpingstation-simulations-harness.md

@@ -1,8 +1,8 @@
-# DECISION-20260422-pumpingstation-eval-harness
+# DECISION-20260422-pumpingstation-simulations-harness
 
 ## Context
 - Task/request: Provide a way to fluctuate inputs to the pumpingStation and observe the system's response over time, in a readable form suitable for post-hoc analysis (operator review, Grafana, or ad-hoc debugging).
-- Impacted files/contracts: `nodes/pumpingStation/eval/*`, `test/basic/*`.
+- Impacted files/contracts: `nodes/pumpingStation/simulations/*`, `test/basic/*`.
 - Why a decision is required now: Unit tests (`node --test`) verify individual functions in isolation. They can't ergonomically show "what does the level look like over 20 minutes of storm surge". That's a different artefact.
 
 ## Options
@@ -10,7 +10,7 @@
 - Benefits: Single testing surface.
 - Risks: Unit tests are assertion-heavy and slow to read; scenario output (tables, events) gets lost in TAP.
 
-2. Separate `eval/` folder with a scenario runner (selected)
+2. Separate `simulations/` folder with a scenario runner (selected)
 - Benefits: Scenarios read as narratives ("steady state", "storm surge", "safety dry-run"); output is human-friendly (ASCII table + events + expectation checks); JSONL per-tick log enables Grafana streaming or offline analysis.
 - Risks: Second test surface to maintain.
 
@@ -22,14 +22,18 @@
 - Selected option: Option 2.
 - Decision owner: User
 - Date: 2026-04-22
-- Rationale: Unit tests answer "is this function correct?"; evals answer "how does the system behave under this input profile?". Two distinct questions — two distinct tools. The split also matches the .claude/rules/testing.md 3-tier convention (basic/integration/edge) which is for asserted behaviours, not scenario replay.
+- Rationale: Unit tests answer "is this function correct?"; scenarios answer "how does the system behave under this input profile?". Two distinct questions — two distinct tools. The split also matches the .claude/rules/testing.md 3-tier convention (basic/integration/edge) which is for asserted behaviours, not scenario replay.
+
+### Addendum (same-day rename)
+
+Folder was initially named `eval/`. Renamed to `simulations/` in commit pumpingStation@3e13512 — `eval` and `test` are near-synonyms so the split implied a conceptual difference that doesn't really exist. `simulations/` is more honest about what's happening (scripted plant inputs driving a physics sim, recorded for analysis). Rationale above is unchanged; only the folder name is.
 
 ## Architecture
 
 ```
 test/
   basic/ integration/ edge/   — node:test + assertions
-eval/
+simulations/
   run.js                      — scenario driver
   scenarios/*.js              — each exports { name, config, setup, inputs(t,ps), expectations }
   formatters/table.js         — ASCII summary
@@ -42,12 +46,12 @@ Driver monkey-patches `Date.now()` so the volume integrator sees 1 second per ti
 ## Consequences
 - Compatibility impact: None.
 - Safety/security impact: None — read-only simulation.
-- Data/operations impact: Running `node eval/run.js --all` produces artefacts that can be checked into CI for regression (e.g. "did the storm scenario's max level rise compared to last release?"). The JSONL format is friendly to InfluxDB/Grafana for interactive review.
+- Data/operations impact: Running `node simulations/run.js --all` produces artefacts that can be checked into CI for regression (e.g. "did the storm scenario's max level rise compared to last release?"). The JSONL format is friendly to InfluxDB/Grafana for interactive review.
 
 ## Implementation Notes
-- Required code/doc updates: Driver + three starter scenarios (`levelbased-steady`, `levelbased-storm`, `safety-dry-run-trip`) + README in `eval/`.
+- Required code/doc updates: Driver + three starter scenarios (`levelbased-steady`, `levelbased-storm`, `safety-dry-run-trip`) + README in `simulations/`.
-- Validation evidence required: `node eval/run.js --all` exits 0; manual inspection of JSONL confirms per-tick records make physical sense.
+- Validation evidence required: `node simulations/run.js --all` exits 0; manual inspection of JSONL confirms per-tick records make physical sense.
 
 ## Rollback / Migration
-- Rollback strategy: Delete `eval/`. Unit tests continue to work.
+- Rollback strategy: Delete `simulations/`. Unit tests continue to work.
 - Migration/deprecation plan: N/A.