fix(sandbox): PR-B fold-ins — allow read ~/.claude + skip wrap under test mock

Live PI231 verification of d0dcd28 surfaced two real-runtime issues:

1. ~/.claude was denyRead, but claude CLI MUST read its own OAuth
   credentials file to authenticate. Result: 100% of anthropic requests
   on sandboxed PI231 failed with "Not logged in · Please run /login".
   Live transcript:
     {"event":"fallback_hop_error", "provider":"anthropic",
      "error":"Not logged in · Please run /login"}

   The cross-tenant risk for ~/.claude was a false security trade-off:
   (a) ~/.claude is the spawn's OWN auth, not cross-tenant material
       (all OLP clients share the same Anthropic OAuth — the file is
       not multi-tenant secret)
   (b) Real protection for the model accidentally exfiltrating creds
       via tool_use is Phase 6c's --system-prompt suppressing tool
       descriptions; sandbox-runtime can only blanket-deny a path, not
       distinguish "claude reads creds" from "model emits Read tool"
   Fix: remove ~/.claude from denyRead. Keep ~/.olp, ~/.ssh, ~/.config,
   ~/.codex (all genuinely cross-tenant).
   Suite 44a (cat ~/.olp/keys.json MUST fail) unchanged — still proves
   the core acceptance.
   Suite 44c added (regression guard): in-sandbox cat ~/.claude/.credentials.json
   MUST succeed when the file exists.

2. anthropic.mjs::_spawnAndStream called wrapSpawn() unconditionally,
   including when a test had set __setSpawnImpl(mockFn). The wrap
   rewrites bin to '/bin/sh -c <wrapped-string>' which breaks every HTTP
   integration test that asserts on spawn args. Result on PI231 (sandbox
   active): 16 production-shape tests failed because their mocks were
   never called with the expected bin/args.
   Fix: skip wrapSpawn when spawnImpl !== defaultSpawn (mock active).
   Mocks don't exec, so isolation is meaningless there anyway. Real-CLI
   spawns (production + Suite 44) still get wrapped.

Tests: 813 → 813 (44c is also PI231-gated, skips on Mac with file
absent; the fold-in does not change Mac test count).

Authority:
- @anthropic-ai/sandbox-runtime v0.0.52 — wrapWithSandbox() shell-string
  return shape is the proximate cause of (2)
- Live PI231 2026-05-28 transcript: /v1/chat/completions returning
  content=null + "Not logged in" from anthropic; OLP_E2E_SANDBOX=1 npm
  test showing 16 prior pass tests now fail
- ADR 0014 § 4.1 PR-B acceptance criteria — the negative test (44a)
  continues to pass; the false-positive denyRead (~/.claude) is corrected

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/sandbox/manager.mjs

@@ -167,12 +167,30 @@ export async function bootstrapSandbox(opts = {}) {
   // denyRead: Absolute literal Linux paths per ADR 0014 § Pitfalls #2.
   // No ~ or glob — ripgrep glob expansion is not used here to stay safe on
   // both Linux (bwrap) and macOS (sandbox-exec profile).
+  //
+  // 2026-05-28 PR-B fold-in: ~/.claude is NOT in denyRead. It contains the
+  // spawn's own OAuth credentials — claude CLI must read its own auth file
+  // to function. Denying read here causes "Not logged in" failures even
+  // though the operator has valid credentials present.
+  //
+  // The cross-tenant risk for ~/.claude is mitigated by Phase 6c's
+  // --system-prompt flag (ADR 0009 Amendment 1): the system prompt is
+  // fully replaced, suppressing the default tool descriptions that would
+  // otherwise tell the model it has Read/Bash. Without tool descriptions,
+  // the model is highly unlikely to emit tool_use even under prompt
+  // injection. Sandbox's contribution here is protecting OTHER auth
+  // material (other clients' OLP keys, SSH identity, other providers'
+  // tokens) — files claude CLI does NOT legitimately need.
+  //
+  // If we ever switch to a CLI that requires reading credentials.json
+  // AND also legitimately offers tool execution that surfaces those files
+  // (no known case today), this trade-off needs revisiting.
   const denyRead = [
-    join(home, '.olp'),       // OLP API keys + config
-    join(home, '.claude'),    // Claude OAuth credentials
-    join(home, '.ssh'),       // SSH identity material
+    join(home, '.olp'),       // OLP API keys + config — cross-tenant
+    join(home, '.ssh'),       // SSH identity material — lateral movement
     join(home, '.config'),    // Generic config dir (may contain tokens)
-    join(home, '.codex'),     // Codex config (PR-C will wrap codex)
+    join(home, '.codex'),     // Codex config — other-provider auth (PR-C will wrap codex)
+    // NOT denied: ~/.claude — this spawn's own auth, breaks claude CLI if denied
   ];
 
   // allowWrite: ephemeral spawn workspace only. mkdirSync at bootstrap.