fix: assert hygiene -- unreachable assert, two caller-facing checks

[petercorke]

Summary

Found while surveying src/'s ~48 Bandit B101 ("assert used") findings (see #99, which excludes tests/ from that check but leaves src/'s real findings active). Most are legitimate -- type-narrowing right after a prior check, or optional-dependency guards immediately following an ImportError raise -- and are staying as-is. Three were real issues:

• Sources.py (PointCloud publish support): assert o3d is not None sat inside the if not _open3d_available: raise ImportError(...) block, after the raise -- unreachable dead code. Apparently a mis-indented copy of the same pattern used correctly at 7 other call sites in this file. Dedented to match them.
• BundleAdjust.py: add_projection()'s assert len(uv) == 2, "uv must be a 2-vector" validates a caller-supplied argument on a public method, not an internal invariant -- converted to if len(uv) != 2: raise ValueError(...) so it survives python -O instead of silently vanishing.
• Camera.py: nu/nv/width/height each asserted self._imagesize is not None, "imagesize not set" -- a real "you called this before configuring the camera" caller mistake (the informative message was the tell), not an internal invariant. Converted to if self._imagesize is None: raise ValueError(...), matching the existing raise ValueError("imagesize or rho properties not set") convention already used elsewhere in this file (Camera.py:1900).

Test plan

• Full test suite: 1010 passed, 15 skipped, no regressions.

🤖 Generated with Claude Code

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 10 complexity · 0 duplication

Metric	Results
Complexity	10
Duplication	0

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