feat: Add --input scc option for SCC input format

[cfsmp3]

Summary

Add support for --input scc command line option to explicitly specify SCC (Scenarist Closed Caption) input format, for consistency with other input format options.

Before:

$ ccextractor --input scc file.scc
error: invalid value 'scc' for '--input <format>'
  [possible values: ts, ps, es, asf, wtv, bin, raw, mp4, m2ts, mkv, mxf]

After:

$ ccextractor --help | grep -A20 "Input Formats:"
...
          - scc:  Scenarist Closed Caption (SCC)

Changes

• Add Scc variant to InFormat enum in args.rs
• Handle InFormat::Scc in parser.rs to set StreamMode::Scc
• Add StreamMode::Scc case in print_cfg() in both Rust (demux.rs) and C (ccx_demuxer.c)

Test plan

• --help shows scc as valid input format
• --input scc accepted without error
• SCC files processed correctly with explicit format
• All 265 Rust unit tests pass

Fixes #1972

🤖 Generated with Claude Code

[ccextractor-bot]

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit f5dc1cf...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	7/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	81/86
Teletext	21/21
WTV	13/13
XDS	34/34

NOTE: The following tests have been failing on the master branch as well as the PR:

• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65..., Last passed:

  Test 7572

• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b..., Last passed:

  Test 7572

• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7572

• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7572

• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7572

• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7572

• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7572

This PR does not introduce any new test failures. However, some tests are failing on both master and this PR (see above).

Check the result page for more info.

[ccextractor-bot]

CCExtractor CI platform finished running the test files on windows. Below is a summary of the test results, when compared to test for commit f5dc1cf...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	6/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	80/86
Teletext	21/21
WTV	13/13
XDS	34/34

NOTE: The following tests have been failing on the master branch as well as the PR:

• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2..., Last passed:

  Test 7573

• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65..., Last passed:

  Test 7573

• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b..., Last passed:

  Test 7573

• ccextractor --out=spupng c83f765c66..., Last passed:

  Test 7573

• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7573

• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7573

• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7573

• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7573

• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7573

This PR does not introduce any new test failures. However, some tests are failing on both master and this PR (see above).

Check the result page for more info.