docs(glossary): add 'tap' — named recorded sink stream

Record-reality add: 'tap' is in consistent use across the code
(ColumnarTrace.tap, the --tap flag, the equity/exposure/net_r_equity/
r_equity taps) and the design ledger, but had no glossary entry. The
entry also draws the line the 'tap/sink' shorthand blurs: a sink is
the recording-role node, a tap is the named stream it records.

docs/glossary.md

@@ -263,6 +263,10 @@ The harness's structural parameterization — which strategy, instrument(s), bro
 **Avoid:** param-sweep, parameter sweep
 An orchestration axis varying tuning params (grid or random) within a fixed structure. The inner, param-tuning loop, distinct from the structural experiment matrix.
 
+### tap
+**Avoid:** —
+A named recorded stream produced by a recording `sink` — the addressable label (e.g. `equity`, `net_r_equity`) under which one sink's per-cycle output is persisted as a columnar (SoA) `ColumnarTrace` and selected for charting via `--tap`. Distinct from the `sink` node that emits it (a tap is the stream, the sink is the role) and from a whole recorded run (a bundle of taps); taps fire at their own cadences and are fused only by joining on the recorded timestamp, never by positional index.
+
 ### veto
 **Avoid:** risk-manager
 The **optional** documented pre-trade-gate seam in the execution chain (`stop-rule → [Veto] → position-management`): position / exposure / notional caps that may reject or scale a trade. A pass-through identity DCE'd away when absent (C19/C23); kept as a named seam — it is what LEAN calls "Risk Management" and nautilus the RiskEngine.