[harshalsp07]

In raising this pull request, I confirm the following (please check boxes):

Reason for this PR:

• This PR adds new functionality.
• This PR fixes a bug that I have personally experienced or that a real user has reported and for which a sample exists.
• This PR is porting code from C to Rust.

Sanity check:

• I have read and understood the contributors guide.
• I have checked that another pull request for this purpose does not exist.
• If the PR adds new functionality, I've added it to the changelog. If it's just a bug fix, I have NOT added it to the changelog.
• I am NOT adding new C code unless it's to fix an existing, reproducible bug.

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--scc-framerate 23.976 and its 23.98 alias are accepted by the CLI, but SCC import silently uses 29.97 fps. Both spellings become integer value 4; SccFrameRate::from_int() doesn't handle it and falls back to the default.

Add the missing decoder rate and use 1001 / 24 milliseconds per frame. The other rate mappings stay the same.

Reproduce from the repository root with the included 90-byte sample:

ccextractor tests/samples/scc_23_976.scc --scc-framerate 23.976 -o out.srt

The sample contains HI between 00:00:01:12 and 00:00:03:12. On master d7eb132e, the SRT timing is 00:00:01,401 --> 00:00:03,399. With this change it is 00:00:01,501 --> 00:00:03,499. Repeating with 23.98 gives the same corrected timing.

Tested on Linux:

• cargo test --locked in src/rust: 427 passed. The new SCC parsing test fails without the fix.
• cargo fmt --all -- --check and cargo clippy -- -D warnings pass.
• Release CMake build and 172 CLI runs checking all accepted frame-rate spellings, four frame offsets, BOM/CRLF, explicit SCC input and five output formats. All 70 comparisons for previously supported input and rates are byte-identical to master.

This fixes SCC input parsing. #2145 and #2406 concern CEA-708 SCC output timing. Windows/macOS and the external sample platform haven't been tested.

CI note: The initial Linux build stops before compilation because libgpac-dev has no installation candidate on Ubuntu 26.04; #2428 addresses the runner change. The C format check also flags ccx_decoders_isdb.c and mp4.c, which are unchanged from master.