docs(examples): bump Isaac/Python version refs to Sim 6.0 / py3.12 (closes #103)

[yinsong1986]

What changed

Updates the example-side Isaac Sim / Python version references to match
the Isaac Sim 6.0 / Python 3.12 migration (#101, PR #102), which bumps the
package to requires-python>=3.12 + isaacsim>=6.0.

File	Change
examples/libero/run_isaac.py	Requires install line, verification-status header (docker tag), and the is_available() error-path install hint now reference Isaac Sim 6.0+ / Python 3.12 / nvcr.io/nvidia/isaac-sim:6.0.
examples/libero/run_isaac_agent.py	Same set: status header, --policy=groot host requirement, Requires list entry, and error-path install hint.
examples/isaac_gs/README.md	"GPU-validated" section now names the nvcr.io/nvidia/isaac-sim:6.0 image (Python 3.12) as the target runtime.
examples/mujoco_gs/pyproject.toml	requires-python bumped >=3.10 → >=3.12 for project-wide consistency.

Diff: 4 files, +39 / −19.

Why

PR #102 (open) bumps the library to requires-python>=3.12 + isaacsim>=6.0.
A user following the example docs would install Isaac Sim 4.5 / Python 3.10,
which can no longer satisfy that floor — the install failure tracked in #98.
The dual-path library code (try: isaacsim.* / except ImportError: omni.isaac.*)
still runs on 4.5 at runtime, but the package can no longer be installed on
a 3.10 / 4.5 host, so the example docs were misleading.

Design decisions

• Install directions vs. historical records. Forward-looking install
  directions ("a working Isaac Sim 4.5+ install", error-path hints, the docker
  tag users would pull) were bumped to 6.0 / 3.12. The historical
  "validated end-to-end on 4.5" records were preserved but reframed to name
  6.0 as the target runtime and note the dual-path imports keep the same
  code path working on both 4.5 and 6.0.
• Factual API-compat notes left as-is. Lines like "falls back to the
  legacy omni.importer.urdf for pre-4.5 builds" and "isaacsim.storage.native
  … (Isaac Sim 4.5+ supported path)" are accurate statements about when a
  module path became available; they remain true on 6.0 and were not rewritten.
  This matches the convention stated in PR feat(isaac): migrate omni.isaac.* → isaacsim.* for Isaac Sim 6.0 / Python 3.12 (closes #101) #102 / PR docs(examples): bump so101_curobo Isaac pins to Sim 6.0 / Python 3.12 (closes #104) #105.
• mujoco_gs/pyproject.toml → >=3.12. This is a MuJoCo-only example
  (depends on strands-robots[sim-mujoco], not strands-robots-sim[isaac]),
  so it technically runs on 3.10+. Pinned to >=3.12 for consistency with the
  project-wide floor so every example installs in a single 3.12 environment; a
  comment in the file documents this rationale.

What was intentionally left out (no overlap with #104 / PR #105)

The issue's location list includes two so101_curobo spots
(examples/so101_curobo/scene.py, examples/so101_curobo/requirements.txt).
Those are owned by #104 / PR #105 (which is open and already bumps them),
so they are intentionally untouched here to avoid a merge collision. PR #105's
body explicitly hands the rest of the sweep to #103.

Test surface

• hatch run lint — clean (black + isort + flake8 over strands_robots_sim + examples).
• hatch run test — 203 passed, 33 skipped (skips are GPU/Isaac-gated). No
  new failures. Changes are docs/comment/config only, so no test behavior is
  affected. (The pre-existing environmental skips/failures in
  test_rendering.py / test_policy_runner.py from missing X11/OpenGL on the
  dev box were not triggered by this run and are unrelated to this change.)

Acceptance criteria (issue #103)

• examples/libero/run_isaac.py docstring docker tag → 6.0 / py3.12
• examples/libero/run_isaac_agent.py docstring docker tag → 6.0 / py3.12
• examples/isaac_gs/README.md Isaac Sim 4.5 reference → 6.0 / py3.12
• examples/so101_curobo/scene.py error message — owned by PR docs(examples): bump so101_curobo Isaac pins to Sim 6.0 / Python 3.12 (closes #104) #105
• examples/so101_curobo/requirements.txt docker tag — owned by PR docs(examples): bump so101_curobo Isaac pins to Sim 6.0 / Python 3.12 (closes #104) #105
• examples/mujoco_gs/pyproject.toml >=3.10 — decided: bumped to >=3.12
  for consistency (MuJoCo-only; rationale in inline comment)

Out of scope / follow-ups

• so101_curobo Isaac adapter (PR #68): verify isaacsim.* API + bump docs for Isaac Sim 6.0 / Python 3.12 #104 / PR docs(examples): bump so101_curobo Isaac pins to Sim 6.0 / Python 3.12 (closes #104) #105 owns the so101_curobo spots.
• Live Isaac Sim 6.0 runtime verification of the examples (the
  create_world → … → destroy smoke) requires a 6.0 GPU host (none in this
  env); this PR is scoped to the version-reference inconsistency, not a runtime
  API regression. Tracked alongside R26: Validate examples/libero/run_isaac.py + run_isaac_agent.py end-to-end on the Isaac Sim backend (and fix) #73.
• This is a merge-coordination item with PR feat(isaac): migrate omni.isaac.* → isaacsim.* for Isaac Sim 6.0 / Python 3.12 (closes #101) #102 (the library migration):
  the example pins here are consistent with where feat(isaac): migrate omni.isaac.* → isaacsim.* for Isaac Sim 6.0 / Python 3.12 (closes #101) #102 takes the package and
  are safe to land independently.

Project board

This issue is on the
Strands Labs - Robots board;
please move it to In review.

Closes #103.