feat(libSceNpManager): answer sceNpCheckNpAvailability with no user signed in

[arvindfroi]

What

sceNpCheckNpAvailability threw. It now follows shadPS4 for a console with no user signed in to PSN:

• The signature is shadPS4's (req_id, online_id); the declared third parameter is dropped.
• A null online id returns SCE_NP_ERROR_INVALID_ARGUMENT (0x80550003).
• Any other online id returns SCE_NP_ERROR_USER_NOT_FOUND (0x80550007): no local user has an online id here, as sceNpGetOnlineId already reports the user as signed out, and that is what shadPS4 returns when its online-id lookup finds no user.
• The request id is not checked, as in the other NpManager requests here.

The checks are in GuestNpReachability rather than GuestNpManager, which #1536 and #926 both extend. sceNpGetUserIdByAccountId is left to #1536.

Tested

tools/check_conventions.py --base origin/main passes. Export.cpp and GuestNpReachability.cpp built natively on macOS (Apple clang, arm64, NotImplemented_nid_no_patch stubbed) and the test passes. No x86-64 toolchain on this machine, so the Linux and Windows builds and ctest are left to CI. No title tested.

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 (Claude Code, Claude Opus 5.5)

🤖 Generated with Claude Code

[github-actions]

Progress report (d70b899 → f4084d5)

📈 System libraries: 84.72% (+0.03%, +1 implemented functions)

✅ 1 implemented

Library	Name
libSceNpManager	sceNpCheckNpAvailability

[popcoder565]

Native Windows run, since no Windows results were posted. Setup: Windows 10 (19045), MinGW-w64 GCC 15.2.0 (WinLibs r7), Release. Head f4084d56, merged onto main d70b899 in one build with 38 other PRs that had no Windows run.

• This PR's tests pass: guest_np_reachability. None of them reported skipping a case.
• Full ctest in that build: 519 of 519. That needed local fixes to three other PRs in the batch that don't build or pass on Windows: feat(libc): export scriptingGetMem and scriptingFreeMem from application heap #1611, feat(posix): implement gethostbyname #1796 and feat(zlib): implement sequential libSceZlib decompression #1824 (reported there).

No title was run.

🤖 Addressed by Claude Code

[adriadam10]

Checked against shadPS4's pinned sceNpCheckNpAvailability (null → INVALID_ARGUMENT, no matching user → USER_NOT_FOUND); the test passes and fails without the change. Linux build + ctest on main merged: guest_np_reachability passes; popcoder565's native Windows run also passes it. Merging.