test(confidence-engine): enable live current understanding experiment execution

Extend the CU synthesis experiment helper with a --live flag that
uses the production provider (getProvider from lib/llm/provider.js)
for live model invocation. Preserves deterministic mode unchanged.

Adds 10 new deterministic tests verifying live-mode wiring via
injected mock provider: fixture pass-through, single invocation,
schema correctness, immutability, persistence safety, and regression
of existing deterministic behaviour. Zero network calls in all tests.

Co-Authored-By: Claude Code <noreply@anthropic.com>

docs/experiment-current-understanding-apparatus.md

@@ -1,22 +1,26 @@
-# CU Synthesis Experiment Apparatus — Iteration 3
+# CU Synthesis Experiment Apparatus — Iteration 5
 
 ## Purpose
 
-Deterministic experiment helper for invoking the production `synthesizeCurrentUnderstanding()` function with fixed local input fixtures, without live model calls.
+Deterministic experiment helper for invoking the production `synthesizeCurrentUnderstanding()` function with fixed local input fixtures, and an explicit live mode for production model execution. Zero live model calls by default.
 
 ## Files
 
 | File | Role |
 |------|------|
-| `scripts/current-understanding-experiment-helper.cjs` | Standalone helper (CJS + dynamic import ESM) |
-| `tests/graph/current-understanding-experiment-helper.test.js` | Deterministic verification (14 tests, 0 live calls) |
+| `scripts/current-understanding-experiment-helper.cjs` | Standalone helper (CJS + dynamic import ESM) — supports both deterministic and live modes |
+| `tests/graph/current-understanding-experiment-helper.test.js` | Deterministic verification (24 tests, 0 live calls) |
 
 ## Usage
 
 ### Helper (CLI)
 
 ```bash
+# Deterministic mode (default — zero live model calls)
 node scripts/current-understanding-experiment-helper.cjs --file fixtures/cu-synthesis.json
+
+# Live production mode (uses configured OLLAMA_MODEL from .env.local)
+node scripts/current-understanding-experiment-helper.cjs --live --file fixtures/cu-synthesis.json
 ```
 
 Fixture contract: `{ situationGraph: object, findings: array }`
@@ -33,6 +37,7 @@ npx vitest run tests/graph/current-understanding-experiment-helper.test.js --env
 - Environment loading via `@next/env` `loadEnvConfig` (proven in both existing helpers)
 - `.env.local` ownership of `OLLAMA_BASE_URL` and `OLLAMA_MODEL` preserved — helper reads from `process.env`, never writes
 - Deterministic inline test double provider pattern (mirrors `makeFakeProvider` in `tests/graph/current-understanding-synthesis.test.js`)
+- Live production provider construction via `getProvider()` imported from `lib/llm/provider.js` (canonical seam, first extraction at line 87-90 of experiment helper)
 
 ## Production Entry Point
 
@@ -45,13 +50,43 @@ Output: `{ currentUnderstanding: string }`
 
 ## Verification Results
 
-All 14 deterministic tests PASS. Zero live model calls. The following invariants verified:
+All 24 deterministic tests PASS. Zero live model calls. The following invariants verified:
 - Fixed compatible input reaches `synthesizeCurrentUnderstanding()`
 - Expected structured output `{ currentUnderstanding }` captured
 - Prompt includes revised Rule 2 boundary text ("Do not introduce or describe open questions...")
 - Exactly one synthesis invocation per run
 - Input fixture is not mutated (deep clone + compare)
 - No persistence/Supabase/DB operations
+- Live-mode wiring verified via deterministic injected mock provider
+- Deterministic mode behaviour preserved unchanged
+
+## Iteration 5 — Live Provider Seam
+
+### New seam: `createLiveProvider()` in `scripts/current-understanding-experiment-helper.cjs` (line 87-90)
+
+Reuses the canonical provider construction from `lib/llm/provider.js`:
+```js
+const { getProvider } = await import(PROJECT_ROOT + "/lib/llm/provider.js");
+return getProvider();
+```
+
+### New CLI flag: `--live`
+
+When `--live` is specified alongside `--file`, the helper uses the production provider instead of the test double. Requires `OLLAMA_BASE_URL` and `OLLAMA_MODEL` from `.env.local`.
+
+### Test coverage for live-mode (10 new tests)
+
+All 10 tests use a deterministic injected mock provider (no network). They verify:
+1. Fixture passes through unchanged to synthesis function
+2. Provider seam invoked exactly once
+3. Evidence projection passed as prompt with correct headers
+4. Current Understanding text captured correctly
+5. Schema matches `synthesisOutputSchema`
+6. No persistence operations
+7. Deterministic mode still works (regression)
+8. Rule 2 boundary text present
+9. Zero I/O in tests (mock is pure function)
+10. Full apparatus output shape validated for live-mode path
 
 ## Iteration 4 — Regression Fixture