Fix Colab huggingface-hub conflict, ensurepip fallback, bump to 2026.3.14 (#4603)

* Fix Colab huggingface-hub conflict, ensurepip fallback, bump to 2026.3.14

- colab.py / setup.sh: relax == pins to >= when installing studio.txt
  on Colab so huggingface-hub does not clobber Colab's bundled version
  (breaks transformers is_offline_mode import)
- install_python_stack.py: when uv is unavailable and pip is missing
  (uv-created venvs), bootstrap via ensurepip before attempting upgrade
- Bump version to 2026.3.14
- Bump installer min version pins to 2026.3.14

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

studio/install_python_stack.py

@@ -373,11 +373,29 @@ def install_python_stack() -> int:
             ],
         )
     else:
-        run(
-            "Upgrading pip",
-            [sys.executable, "-m", "pip", "install", "--upgrade", "pip"],
+        # pip may not exist yet (uv-created venvs omit it). Try ensurepip
+        # first, then upgrade. Only fall back to a direct upgrade when pip
+        # is already present.
+        _has_pip = (
+            subprocess.run(
+                [sys.executable, "-m", "pip", "--version"],
+                stdout = subprocess.DEVNULL,
+                stderr = subprocess.DEVNULL,
+            ).returncode
+            == 0
         )
 
+        if not _has_pip:
+            run(
+                "Bootstrapping pip via ensurepip",
+                [sys.executable, "-m", "ensurepip", "--upgrade"],
+            )
+        else:
+            run(
+                "Upgrading pip",
+                [sys.executable, "-m", "pip", "install", "--upgrade", "pip"],
+            )
+
     # 3. Core packages: unsloth-zoo + unsloth (or custom package name)
     if skip_base:
         print(_green(f"✅ {package_name} already installed — skipping base packages"))