AUv2: a failed idle-time reactivation leaves the CLAP state machine violated

[defiantnerd]

Found while fixing AUV2-1 (stale audio during a plugin-requested restart) in the 0.16 release review. Not fixed there — it is a distinct defect on the same path.

The problem

In src/wrapasauv2.cpp, onIdle()'s restart path:

• activateCLAP() ignores the return value of Plugin::activate().
• deactivateCLAP() calls stop_processing() and deactivate() unguarded.

So if a plugin-requested restart fails to reactivate, _initialized stays false and the wrapper carries on. A later AU Uninitialize then calls stop_processing()/deactivate() on a plugin that is already inactive — which CLAP's state machine does not allow.

The onIdle comment acknowledges the failure is possible ("If it fails anyway, _initialized stays false…"), but nothing records that the CLAP is now down as opposed to running but not initialized, and the teardown path cannot tell the two apart.

Suggested fix

Track CLAP activation state explicitly rather than inferring it from _initialized, and make deactivateCLAP() a no-op when the plugin is not active. activateCLAP() should propagate the failure so the caller can decide, rather than discarding it.

[defiantnerd]

Fixed in #564, merged to next as d48f9c6.

_clapActive now records the fact _initialized was being asked to stand in for — it conflated "the CLAP is down" with "running but not initialized", which is why the teardown path could not tell them apart. activateCLAP() propagates clap_plugin.activate()'s failure and tears its own process adapter back down on the way out, so nothing queues on an adapter no flush will drain; deactivateCLAP() guards stop_processing()/deactivate() on it.

Follow-on, deliberately not fixed here: Plugin::start_processing() also returns a bool that is ignored, so a plugin that activates but refuses to start processing still gets _initialized = true and a process() call. That needs a second, processing-level state, since stop_processing() would then be illegal too — same family as this issue, but not what it describes.