fix(memory): fall back to pip when uv is unavailable (salvage #5954) (#38668)

`_install_dependencies` (hermes memory setup) hard-aborted with
"uv not found — cannot install dependencies" whenever `uv` was not on
PATH, even when a perfectly good `pip` was available. Slim container
images and some CI environments don't ship uv, so memory-provider
dependency installation dead-ended there for no good reason.

Now: use `uv pip install` when uv is present, otherwise fall back to
`<python> -m pip install` when pip3/pip is available, and only abort
(with the uv install hint) when neither is found. The "Run manually:"
hints reflect whichever installer was selected.

Salvages #5954 by @MustafaKara7. Their patch added redundant local
`import subprocess` / `import sys` (both are already in scope — module
-level `sys`, function-top `subprocess`); this salvage drops those and
adds a regression test (TestInstallDependenciesRunner) covering all
three paths (uv / pip-fallback / abort). Verified adversarially: the
pip-fallback test fails against origin/main's unfixed code with the
exact dead-end symptom and passes with the fix.

Closes #5954.

Co-authored-by: MustafaKara7 <186085093+MustafaKara7@users.noreply.github.com>

hermes_cli/memory_setup.py

@@ -97,16 +97,25 @@ def _install_dependencies(provider_name: str) -> None:
     print(f"\n  Installing dependencies: {', '.join(missing)}")
 
     import shutil
+
     uv_path = shutil.which("uv")
-    if not uv_path:
-        print(f"  ⚠ uv not found — cannot install dependencies")
-        print(f"  Install uv: curl -LsSf https://astral.sh/uv/install.sh | sh")
-        print(f"  Then re-run: hermes memory setup")
-        return
+    if uv_path:
+        install_cmd = [uv_path, "pip", "install", "--python", sys.executable, "--quiet"] + missing
+        manual_cmd = f"uv pip install --python {sys.executable} {' '.join(missing)}"
+    else:
+        pip_cmd = shutil.which("pip3") or shutil.which("pip")
+        if not pip_cmd:
+            print(f"  ⚠ uv not found — cannot install dependencies")
+            print(f"  Install uv: curl -LsSf https://astral.sh/uv/install.sh | sh")
+            print(f"  Then re-run: hermes memory setup")
+            return
+        print(f"  ⚠ uv not found. Falling back to standard pip...")
+        install_cmd = [sys.executable, "-m", "pip", "install", "--quiet"] + missing
+        manual_cmd = f"{sys.executable} -m pip install {' '.join(missing)}"
 
     try:
         subprocess.run(
-            [uv_path, "pip", "install", "--python", sys.executable, "--quiet"] + missing,
+            install_cmd,
             check=True, timeout=120,
             capture_output=True,
         )
@@ -116,10 +125,10 @@ def _install_dependencies(provider_name: str) -> None:
         stderr = (e.stderr or b"").decode()[:200]
         if stderr:
             print(f"    {stderr}")
-        print(f"  Run manually: uv pip install --python {sys.executable} {' '.join(missing)}")
+        print(f"  Run manually: {manual_cmd}")
     except Exception as e:
         print(f"  ⚠ Install failed: {e}")
-        print(f"  Run manually: uv pip install --python {sys.executable} {' '.join(missing)}")
+        print(f"  Run manually: {manual_cmd}")
 
     # Also show external dependencies (non-pip) if any
     ext_deps = meta.get("external_dependencies", [])