feat(libSceAgc): implement DCB and ACB marker span functions

[Kikoarl]

What

Implements sceAgcDcbPushMarkerSpan, sceAgcDcbSetMarkerSpan, sceAgcAcbPushMarkerSpan, and sceAgcAcbSetMarkerSpan in libSceAgc.

• Provenance: Signatures (cb, marker, length, color) follow OpenAGC (include/agcdriver.h and src/cb_builders.c), which document the explicit-length marker variants for DCB and ACB.
• Sits symmetrically alongside existing sceAgcDcbPushMarker, sceAgcDcbSetMarker, sceAgcAcbPushMarker, and sceAgcAcbSetMarker.
• Emits the standard custom NOP marker packet (0x10, sub-opcode 0x0b for push, 0x0c for pop) with explicit length bounds, ensuring payload zero-padding and null-termination.
• Validates command buffer pointers and rejects null text when length is non-zero with an exact-or-throw policy.
• Documented in TechnicalDebt.md in the same commit.

Tested

• Built cleanly on Linux with GCC in /tmp/anyps5_build.
• Unit tests added to core/libs/prx/libSceAgc/tests/Commands.cpp (testMarkers in agc_commands):
  • Verified packet header, sub-opcode, text payload, and cursor advance for DCB and ACB PushMarkerSpan.
  • Verified SetMarkerSpan emits matching push and pop packets for DCB and ACB.
  • Verified empty marker with length 0 and null pointer.
  • Negative tests verify rejection of null command buffers and null text with non-zero length.
  • Passed ctest -R agc_commands.
• Progress: python3 tools/progress.py confirms libSceAgc progress improved from 199 to 202 implemented functions (4 stubs resolved).

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw (NotImplemented_nid_no_patch); silent stubs are listed in TechnicalDebt
• No notes, investigation .md files or images added to the repository (attach them to this PR)
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: none
• AI-assisted: yes

[github-actions]

Progress report (a9ec7be → de52e0e)

📈 System libraries: 87.44% (+0.14%, +4 implemented functions)

✅ 4 implemented

Library	Name
libSceAgc	sceAgcAcbPushMarkerSpan
libSceAgc	sceAgcAcbSetMarkerSpan
libSceAgc	sceAgcDcbPushMarkerSpan
libSceAgc	sceAgcDcbSetMarkerSpan

[github-actions]

Other open pull requests touch the same code. Merging one will break the other, or both implement the same thing. If this one builds on them, list them in Depends on.

Pull request	Conflicting files (lines on main)	Same exports	Same new files
#971	core/libs/prx/libSceAgc/DcbState/src/Marker.cpp L22, L24-25, L31, L34, L62	sceAgcAcbPushMarkerSpan sceAgcAcbSetMarkerSpan sceAgcDcbPushMarkerSpan sceAgcDcbSetMarkerSpan
#1061	docs/dev/TechnicalDebt.md L33

[oneandonlydean]

Thanks for the PR. I'm closing this one, for two reasons:

• feat(libSceAgc): implement the marker span builders #971 already implements the same four functions (sceAgc{Dcb,Acb}{Push,Set}MarkerSpan) in the same files and was opened first, so these two would conflict and only one can go in. If you see a problem with feat(libSceAgc): implement the marker span builders #971's version, a review comment there is the best place for it.
• As with feat(libSceNpSessionSignaling): implement sceNpSessionSignalingGetConnectionStatistics #970 and feat(libSceVoiceQoS): implement sceVoiceQoSEnd #999, no title is shown to reach these on main. The owner merges library functions only when a title needs them, shown by the title ID and the log line where it stops on main.

If a title stops at one of the marker span functions on main, please add the title ID and that log line on #971.