fix: keep local home paths and addresses out of the test fixtures [skip release]

Three test-only spots had baked in the machine this repository was developed
on, and the repository is publicly readable, so they shipped that machine's
shape to anyone who cloned it:

  * the end-to-end embedding backend was pinned to a private LAN address;
    it is now read from DSH_SLOPO_E2E_API_BASE, defaulting to Ollama's own
    loopback address, so the machine running the suite supplies its own;
  * the real-slopo test resolved discovery from a hardcoded root home, which
    meant it could only ever run for one user — it resolves from the running
    user's home now, which is also the fix for everyone else;
  * the harness-slot contract tests read the global npm tree by absolute
    path; they go through this repository's own node_modules symlink, which
    is already relative to the checkout.

No user-facing behaviour changes and the published package never contained
the test files, so this push publishes nothing. The default configuration was
already free of machine-specific values: every address, path and key defaults
to empty and is resolved per user at runtime.

[skip release]

test/client.test.js

@@ -31,11 +31,18 @@ import assert from 'node:assert/strict'
 import { existsSync, readFileSync } from 'node:fs'
 import { join } from 'node:path'
 import { test } from 'node:test'
+import { fileURLToPath } from 'node:url'
 
 const SOURCE = readFileSync(new URL('../client/client.js', import.meta.url), 'utf8')
 
-/** Where a global dsh installation keeps its packages, if there is one. */
-const DSH_PACKAGES = '/usr/local/lib/node_modules/@deepseek-ai/dsh/node_modules/@deepseek-ai'
+/**
+ * The installed harness's packages, reached through this repository's own
+ * `node_modules/@deepseek-ai` symlink rather than a committed absolute path —
+ * the link is what makes the `@deepseek-ai/*` imports resolve during tests in
+ * the first place, so it is the one address that is already relative to the
+ * checkout.
+ */
+const DSH_PACKAGES = fileURLToPath(new URL('../node_modules/@deepseek-ai/', import.meta.url))
 
 // ---------------------------------------------------------------------------
 // The two doubles