Docs: reconcile to two-scope capture model (master removed)

Update the CLAUDE.md FX-scope invariant to item+track only; note master
removal in COMPLETED.md; drop master references from the tail spec and PLAN
Milestone T; realtime now taps the selected track.

CLAUDE.md

@@ -85,4 +85,4 @@ There is no hot-reload. Copy the built binary into REAPER's `UserPlugins/` folde
 - **Non-destructive:** capture never mutates source items or tracks; the realtime backend's temp track is created and removed cleanly, and source routing is restored.
 - **Exact bounds:** no rounding of the requested range; no added silence unless a tail is explicitly requested; channel count preserved (no silent stereo fold).
 - **Relative paths only** in the persisted `BankIndex`.
-- **Capture FX scope:** item capture = item/take FX only; track capture = item + the track's own FX; master = full chain. For item/track, the out-of-scope chain (ancestors + master, plus the item's own track for item scope) is rendered with its FX, gain, and pan/width/pan-law/mode neutralized to unity — so captures are uncolored by, and independent of, the parent/folder/master chain. Range (time selection or razor) is orthogonal.
+- **Capture FX scope:** two scopes only — item = item/take FX only; track = item FX + the selected track's own track FX. There is no master scope (to capture the master, render a track instead). For both scopes, the out-of-scope chain (ancestors + master track, plus the item's own track for item scope) has its FX, gain, and pan/width/pan-law/mode neutralized to unity — the master track is bypassed as out-of-scope chain, not captured as a scope. Range (time selection or razor) is orthogonal.