Plugins: discover supported VST3 channel layouts

[emaspa]

Changes

• Discover the mono/stereo layouts a VST3 plugin actually accepts instead of treating its default bus width as its only layout.
• Offer compatible effects on XLR mic chains and use the same capability rule in the host, catalogue, picker and command validation.
• Preserve old-daemon/cache behavior when width metadata is absent; an explicitly empty supported-width list does not fall back to port counts.
• Validate same-id replacements against the new plugin, while allowing existing incompatible entries to be removed.
• Extend lifecycle diagnostics with channel count, tone frequency and parameter settings. Keep the De-Esser editor compatibility block unchanged.

Verification

• EQ 1.3.0.110, Compressor 1.0.1.142, Noise Removal 1.1.2.119 and De-Esser 1.0.1.133 all negotiated true mono and stereo.
• Non-default processing verified in isolated mono instances: EQ low cut attenuated the tone to zero; Compressor reduced peak 0.250 to 0.004; Noise Removal gated it to zero; De-Esser reduced a 6 kHz tone from 0.234 to 0.034. Stereo results matched.
• Stereo-only Dragonfly Plate Reverb remains stereo-only. The LSP module retained its layout split, with about 0.2 seconds extra on a 17-second scan.
• Combined native-enabled build: 0 warnings/errors, 530 tests passed, 3 opt-in desktop tests skipped. Native audio, CLAP and editor tests passed.
• Width tests also pass without a native helper installed, matching clean CI ordering.
• Local deployment advertises [1,2] for all four Elgato effects. Elgato EQ was observed running on XLR 1 without error, and local testing was confirmed working. De-Esser's native editor remains blocked.

One Noise Removal test's Wine child exited with status 58 at unload after processing and editor checks completed; this was not reproduced in the other runs. No system Wine changes, version bump or release changes.