feat(sandbox): Phase 7 Solution 1 implementation + opus 4.8 (#68)

Implements ADR 0014 Amendment 1 (4-layer Solution 1) + ADR 0002 Amendment 9 (Provider ISOLATION contract) + opus 4.8 model.

Fresh-context opus reviewer APPROVE_WITH_MINOR; 2 nit fold-ins applied. 813 unit tests pass.

Known deferred coverage: Suite 44 PI231 E2E tests are placeholders under describe.skip pending Task #9 (PI231 prod-target validation). The load-bearing negative test ('in-sandbox cat ~/.olp/keys.json MUST fail') will be validated when Task #9 runs against the merged code.

PR-B outer-bwrap superseded; archive at phase-7-pr-b-outer-bwrap-snapshot branch.

models-registry.json

@@ -44,6 +44,14 @@
       "tier": "D",
       "candidate": true,
       "models": [
+        {
+          "id": "claude-opus-4-8",
+          "displayName": "Claude Opus 4.8",
+          "contextWindow": 200000,
+          "deprecated": false,
+          "created": 1783814400,
+          "_comment": "claude-opus-4-8 added 2026-05-29 (Task #15). Model id confirmed via Anthropic published model lineup. `created` set to 1783814400 (2026-07-10) — strictly later than claude-opus-4-7's 1782864000 so OpenAI-spec /v1/models 'created' ordering reflects release recency. If a primary-source Anthropic announcement URL becomes available, replace this placeholder with the announcement timestamp."
+        },
         {
           "id": "claude-opus-4-7",
           "displayName": "Claude Opus 4.7",
@@ -69,7 +77,7 @@
       "aliases": {
         "claude": "claude-sonnet-4-6",
         "sonnet": "claude-sonnet-4-6",
-        "opus": "claude-opus-4-7",
+        "opus": "claude-opus-4-8",
         "haiku": "claude-haiku-4-5"
       }
     },