fix: resolve both operands in metadata path-within-root checks

[mikehardy]

Hey @groove-max 👋

I think this is the separate path-within-root fix you were hoping for when you said that change looked good but should not ride along with the short-ASCII work.

Why

_is_within_root was resolving only one side of the comparison, so symlink forms could disagree with the real containment check. This resolves both operands (path and root) via Path.resolve() + is_relative_to, and adds tests for:

1. Symlink alias acceptance (same file, different path forms)
2. Symlink escape rejection (in-root link pointing outside the root)

Touched only the three metadata helpers + tests/test_local_metadata.py. No short-ASCII in this PR.

Context

Just getting around to processing your MX3 / PR45 feedback and reshaping the stack into smaller pieces. I'm still qualifying the inverter-side work locally over more days of data collection, so the bigger short-ASCII slices will follow separately rather than landing as one blob.

Base is current main (2a945cc at open). Happy to adjust if you'd rather see this shaped differently.

Test plan

• python -m unittest tests.test_local_metadata (15 OK)
• CI green on this PR

Cheers

[groove-max]

Thanks, Mike — I reproduced the error with a symlinked config directory and
verified your fix. I also added tests for draft creation/loading and rejecting
paths outside the metadata root.

Your commits are now included in main, separately from the inverter work in
#45. The fix will be part of the next release.