fix(skills): name the silent bake failure and check the bake result

[TMHSDigital]

Closes #356.

Measured

Live run, --factory-startup, Cycles CPU, 1 sample, a cube bake set up as the skill describes. Binaries report 5.2.1 LTS and 4.5.11 LTS; results are identical on both:

Setup	bpy.ops.object.bake(...)
Correct	{'FINISHED'}; image written (blue mean 1.0)
Low has no UV layer	raises RuntimeError: Error: No active UV layer found in the object "Low"
Lone Image Texture node, not nodes.active	{'FINISHED'}; still baked into it (blue mean 1.0)
Material has no Image Texture node	{'CANCELLED'}, no exception, nothing written

The skill had claimed the UV and non-active-node cases "finish without error". The truly silent one is the missing image node, which nothing checked.

Change

• Skill: the misunderstanding paragraph now carries the measured table and says to check the returned set. The canonical call raises if result != {'FINISHED'}.
• snippets/bake_normal_high_to_low.py: raises on a non-FINISHED result and returns it otherwise (36 lines).

Evidence for the snippet change (live, both versions)

• Correct setup: {'FINISHED'}.
• Same setup without the image node: RuntimeError bake did not finish: {'CANCELLED'}. Before this change it returned {'CANCELLED'} silently.

check_frontmatter passes.

🤖 Generated with Claude Code

[TMHSDigital]

CI evidence before merge: all checks pass ( 13 pass ). Blender Smoke on PR head: Blender 5.2.2 LTS / Blender 4.5.14 LTS. Summaries (happy path; falsifiers) per leg: 143 passed, 1 skipped, 0 failed;143 passed, 0 skipped, 0 failed;141 passed, 3 skipped, 0 failed;136 passed, 7 skipped, 0 failed;