Implement Stage A: rule engine, validation, audit, and safety gates

Completes 109 of 121 tasks. Every remaining task needs a tenant connection
(T055, T056, T101-T103) or an Azure Automation account (T115-T121).

  354 offline Pester tests      PASS
  Engine purity (Principle IV)  PASS
  Sanitization (SC-013)         PASS  (156 files)
  Graph module loaded in tests  none  (SC-008 holds)

What landed
  - Four-layer configuration validation with stable finding codes, covering
    every VR-002 and VR-003 condition, plus a 23-fixture invalid-config corpus
  - Run loop, audit records (NDJSON through a single sink), summaries,
    reconciliation, and exit codes 0-6
  - Persistence behind a single write-body builder whose result always has
    exactly one key
  - Invoke-PersonaEngine.ps1 and Edit-PersonaEngineConfig.ps1
  - Six docs, two pipelines, traceability matrix, V-5a and sanitization records

Three deviations from tasks.md, each recorded in its status block

  T033 is not in Resolve-UserPersona. evaluationErrorThreshold is run-level
  state and the rule engine is pure; a counter there would break Principle IV.
  It lives in New-PersonaRunCounter and is applied in the run loop.

  A new src/Engine/ layer holds Invoke-PersonaEngineRun. The entry script
  imports the manifest, which requires Microsoft.Graph.Authentication, so a
  loop living only inside it could not run on a machine without the Graph SDK
  and SC-004 could not be proven at all. The entry script is now a thin
  wrapper and what ships is what is tested.

  The invalid-config corpus is generated by a committed script, with the
  generated fixtures committed too, so a reviewer sees the fixture in the diff.

Defects found by running the code, not by reading it

  Group and role ID lists were double-wrapped: @(Get-PersonaGroupIdPage ...)
  around a comma-returned array collapsed every membership list into one
  bogus space-joined entry. That is a silent false non-match, exactly what
  FR-013 exists to prevent.

  A 403 whose status appears only in the exception message parsed as $null,
  which the retry policy treats as a transport error - five requests per
  account against a tenant already refusing. Status extraction now falls back
  to the message text, bounded to 400-599.

  The sanitization scan walked tracked files only, so it covered 34 of 156
  files and none of this phase's code. It now scans untracked non-ignored
  files too, and a negative control confirms it catches a planted leak.

  Test-Json reports one error per violating location, not first-failure-only
  as the V-5a draft claimed. Record and pin corrected.

Enforcement remains blocked on the V-4 security sign-off.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

specs/001-persona-engine/verification/V-5a.md

@@ -0,0 +1,57 @@
+# V-5a — `Test-Json -SchemaFile` failure behaviour (local PowerShell)
+
+**Status**: CLOSED
+**Date**: 2026-08-20
+**Environment**: PowerShell 7.6.5, Windows 11, local workstation (Stage A1 — offline, no tenant)
+**Task**: T061
+**Pinned by**: [tests/Configuration/TestJsonBehaviour.Tests.ps1](../../../tests/Configuration/TestJsonBehaviour.Tests.ps1)
+
+## Question
+
+OTD-005 selected `Test-Json -SchemaFile` for layer 2 validation. The documented risk was that
+`Test-Json` reports schema failure inconsistently across PowerShell versions — returning `$false`,
+writing a non-terminating error, or throwing. Layer 2 cannot be written until the actual behaviour
+on the target build is observed rather than assumed.
+
+## Observed behaviour
+
+| Scenario | Return value | Error stream | Terminating? |
+| --- | --- | --- | --- |
+| Valid document | `$true` | empty | no |
+| Type mismatch (`"a": 123` against `"type": "string"`) | `$false` | 1 error: `The JSON is not valid with the schema: Value is "integer" but should be "string" at '/a'` | no |
+| Missing required property | `$false` | 1 error: `The JSON is not valid with the schema: Required properties ["a"] are not present at ''` | no |
+| **Schema file itself unparseable** | **`$true`** | 1 error: `Cannot parse the JSON schema.` | no |
+
+Exception type on the error record is `System.Exception` in every failing case — there is no
+distinct exception type to branch on, so the wrapper must branch on the message text or, better, on
+error presence alone.
+
+## Findings that shape the implementation
+
+1. **Non-terminating, not throwing.** With the default `$ErrorActionPreference = 'Continue'` the
+   cmdlet writes to the error stream and execution continues, returning `$false`. It does not throw.
+   `-ErrorAction SilentlyContinue -ErrorVariable` is therefore sufficient to capture failures, as
+   the editor contract requires.
+
+2. **An unparseable schema returns `$true`.** This is the load-bearing observation. A wrapper that
+   trusted the return value alone would report a configuration as schema-valid when the schema never
+   ran. Layer 2 MUST treat "error variable is non-empty" as failure regardless of the return value,
+   and MUST distinguish the `Cannot parse the JSON schema.` message so it can surface exit code 4
+   (schema file not found or itself invalid) rather than exit code 1 (configuration invalid).
+
+3. **One error per violating location, but not exhaustive.** Two independent property violations
+   yield two error records, each with its own JSON pointer. Deeper or nested subschema failures may
+   still be reported as a single error at the outermost failing location. The wrapper therefore
+   emits one finding per collected error rather than assuming a single one, and the author may still
+   need more than one validation pass to see everything. That residual limitation is documented
+   rather than worked around — full violation reporting would require replacing `Test-Json` with a
+   third-party validator, which OTD-005 rejected.
+
+## Consequences recorded elsewhere
+
+- Layer 2 implementation: [src/Configuration/Test-PersonaConfiguration.ps1](../../../src/Configuration/Test-PersonaConfiguration.ps1)
+- Regression pin: `tests/Configuration/TestJsonBehaviour.Tests.ps1` fails if a future PowerShell
+  build changes any row of the table above.
+- **V-5b remains open**: this observation is for PowerShell 7.6.5 only. The Azure Automation runtime
+  version is unverified, and finding 2 in particular is version-sensitive. Re-run this probe there
+  before Stage B (T116).