docs: close three review nits — the build-shape index, a redundant header restatement, and the CMake guard comment

Bump the product doc's track count and list for T3; trim the header's
pre-limiter restatement now that bake_render.cpp carries it; add limiter
to the extension's not-linked enumeration.

src/core/instrument/bake/bake_render.h

@@ -31,9 +31,8 @@ struct BakeAudio {
 
 // Renders `plan` through `sample`'s own voice path and then the master stage the processor
 // runs after the engine: `masterGainLinear`, then the limiter when `limiterEnabled` — see
-// the master stage in bake_render.cpp for why both are printed here rather than left to the
-// processor. Bypassed, the limiter costs the result not one sample: `limiterEnabled` false
-// is the pre-limiter render, frame for frame. The result is the plan's captured window: the
+// bake_render.cpp for why both print here rather than in the processor. `limiterEnabled`
+// false yields the pre-limiter render. The result is the plan's captured window: the
 // lead-in frames are rendered and dropped. An unplayable sample yields an empty result.
 BakeAudio renderBake(SampleData sample, const BakePlan& plan, double masterGainLinear,
                      bool limiterEnabled);