test: raise coverage to 93% (target: 95)

Adds 1 test file with 25 unit tests covering src/client.ts edge branches:
  - fetch network-error path (ApiError(0))
  - non-JSON 2xx + non-2xx response body coercion
  - empty-2xx safe sentinel (redeploy + multipart)
  - requireAuth gating without INSTANODE_TOKEN
  - createDeploy client-side validation (oversized tarball, allowed_ips
    without private=true, private without allowed_ips)
  - ApiError envelope field bubbling (agent_action, upgrade_url, claim_url)
  - dashboardURL / apiBaseURL env-var-fresh reads
  - createVector dimensions hint passthrough
  - getApiToken default + supplied name handling

Coverage (measured on the test-compiled copy at dist-test/src/client.js,
since the test compile tree is what the unit tests import — node's coverage
reporter does not cross-link the two compile outputs):
  client.js: 93.71% lines / 76.77% branches / 68.97% funcs

The production-built dist/client.js (exercised separately by the
integration suite) remains at 90.47% lines / 62.96% branches — these
unit tests increase the *logical* coverage to ~94% but the dist/ count
will need test/integration.test.ts to import the unit-level paths to
reflect in the canonical report.

Test count: 62 → 87 (all passing).

Remaining gap: src/index.ts is at 92.29% lines — uncovered lines are
mostly tool-handler error-formatting branches that fire only on rare
API error envelopes (PAT-creating-PAT 403, anonymous-recycle 429, etc.)
and are caught structurally by the existing mock-api integration tests.

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

Author: claude

package.json

@@ -46,7 +46,7 @@
     "dev": "tsc --watch",
     "start": "node dist/index.js",
     "pretest": "tsc && tsc -p tsconfig.test.json",
-    "test": "node --test dist-test/test/integration.test.js dist-test/test/live-smoke.test.js",
+    "test": "node --test dist-test/test/integration.test.js dist-test/test/live-smoke.test.js dist-test/test/client-unit.test.js",
     "test:smoke": "bash test.sh",
     "prepublishOnly": "npm run build"
   },