Add cut_diff example: structural editorial diff between two cuts

[chaoz23]

This adds an examples/cut_diff.py script that answers "what changed between cut A and cut B" — which clips were added, removed, retimed, moved, or shifted — in the spirit of existing examples like conform.py and shot_detect.py. The OTIO docs list "Shots Added or Removed From The Cut" as a first-class use case; this example implements it.

Because both inputs go through adapters, the cuts don't need to share a format — an EDL can be diffed against an FCP XML export of the revision:

$ python cut_diff.py editors_cut.edl finishing.fcpxml
1 retimed, 1 shifted (7 unchanged)
  ~ ZZ100_503A shortened by 12f (28f -> 16f)
  . ZZ100_504C shifted 12f earlier

Design notes:

• Clips are matched by identity (media target_url + source in-point), not timeline position — one insertion shifts every downstream timecode, so positional diffing reports everything as changed.
• "Moved" is detected by relative order (longest increasing subsequence over matched clips), so a gap inserted by a lift-trim doesn't read as every downstream clip moving.
• Ripple slides report as "shifted", separate from "retimed", so one trim doesn't read as N retimes.
• Scope is structural editorial only (clips/timing/order); effects and transitions are intentionally out, per their tool-specific serialization.
• --json output and diff(1) exit codes for scripting.

Validated against sample files from the cmx3600 and fcpx-xml adapter test suites, including hand-modified known-change cases. A packaged version with a test suite and an MCP server lives at chaoz23/otio-diff; this example is self-contained.

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[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: chaoz23 / name: chaoz23 (d92cd00)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.58%. Comparing base (73803ef) to head (d92cd00).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2030   +/-   ##
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  Coverage   84.58%   84.58%           
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  Files         181      181           
  Lines       13306    13306           
  Branches     1221     1221           
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  Hits        11255    11255           
  Misses       1868     1868           
  Partials      183      183           

Flag	Coverage Δ
py-unittests	84.58% <ø> (ø)

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