feat(crucible): keep every captured take

With Keep takes on (default), each capture is written to
<folder>/takes/ as a WAV named by time, tempo and length, so a take
is not lost when the next capture replaces it. Files are never
overwritten: a clash gets a numbered suffix. Saving runs off the UI
thread and the status line shows the path or the error.

docs/crucible/CHANGELOG.md

@@ -1,5 +1,12 @@
 # Crucible changelog
 
+## Unreleased
+
+- **Keep takes** (on by default) saves every capture's loop to a `takes`
+  subfolder of the export folder at once. Takes are still not part of the
+  project, but a reload or a crash no longer loses them. Existing files are
+  never overwritten.
+
 ## 0.2.0
 
 - Change the CLAP ID to `io.narl.bass-foundry.crucible`. Hosts see this as a new

docs/crucible/README.md

@@ -52,7 +52,10 @@ the playlist or Edison. **Open folder** shows the latest export in Explorer.
 Crucible adds no latency and passes audio through untouched. Auditioned slices are
 mixed into its output only while they play. The history holds 72 s, enough for
 16 bars at 60 BPM. The newest eight takes stay in memory until the plugin is
-removed; they are not saved with the project, so export what you want to keep.
+removed; they are not saved with the project. With **Keep takes** on (the
+default), every capture's loop is also written at once to
+`takes/<date>_<time>_<tempo>bpm_<bars>bars.wav` in the export folder, so a reload
+or a crash loses nothing. Existing files are never overwritten.
 
 Bar alignment follows the host's song position and time signature. Root notes are
 detected between 35 Hz and 1 kHz. Unpitched slices, such as drums or noise, get