Expand model tag support: add GLM-5.1, simplify Anthropic IDs, scan tags anywhere in message

- Flink update_bars debouncing
- update_bars subscription idempotency bugfix
- Price decimal correction bugfix of previous commit
- Add GLM-5.1 model tag alongside renamed GLM-5
- Use short Anthropic model IDs (sonnet/haiku/opus) instead of full version strings
- Allow @tags anywhere in message content, not just at start
- Return hasOtherContent flag instead of trimmed rest string
- Only trigger greeting stream when tag has no other content
- Update workspace knowledge base references to platform/workspace and platform/shapes
- Hierarchical knowledge base catalog
- 151 Trading Strategies knowledge base articles
- Shapes knowledge base article
- MutateShapes tool instead of workspace patch

gateway/knowledge/trading/strategies/volatility/volatility-carry.md

@@ -0,0 +1,68 @@
+---
+description: "Volatility carry with two ETNs shorts VXX (short-maturity VIX futures ETN) and buys VXZ (medium-maturity VIX futures ETN) to harvest the contango roll loss differential, with the hedge ratio determined by serial regression."
+tags: [volatility, carry, vxx, vxz, etn, contango, roll]
+---
+
+# Volatility Carry with Two ETNs
+
+**Section**: 7.3 | **Asset Class**: Volatility | **Type**: Carry
+
+## Overview
+VXX and VXZ are exchange-traded notes (ETNs) tracking VIX futures. VXX tracks short-maturity (months 1-2) futures and suffers greater roll/contango losses than VXZ (months 4-7), because the VIX futures curve is steepest at the short end in contango. The strategy shorts VXX (captures the larger roll loss as profit) and buys VXZ as a hedge (offsets some exposure to VIX spikes), earning the contango roll differential.
+
+## Construction / Mechanics
+
+**VXX**: tracks a constant-maturity position in months 1-2 VIX futures. Each day, a fraction of the front-month futures is sold and replaced with the next-month futures. In contango, the next-month is more expensive → daily roll loss → VXX decays over time.
+
+**VXZ**: tracks months 4-7 VIX futures. Same roll mechanism but in a less steep part of the contango curve → lower roll loss than VXX.
+
+**Basic strategy**: short VXX, long VXZ.
+
+**Hedge ratio** h (number of VXZ units per VXX shorted):
+```
+h = β = ρ · σ_X / σ_Z
+```
+where:
+- ρ: historical pairwise correlation between VXX and VXZ returns
+- σ_X: historical volatility of VXX
+- σ_Z: historical volatility of VXZ
+- β: slope of serial regression of VXX returns on VXZ returns (with intercept)
+
+The position: short 1 unit of VXX, long h units of VXZ.
+
+## Payoff / Return Profile
+- Earns the differential roll loss between VXX and VXZ: the strategy benefits because VXX decays faster than VXZ in contango.
+- The VXZ long position partially hedges against VIX spikes (which cause VXX to spike more sharply than VXZ).
+- Profitable in normal, low-volatility, contango environments.
+- Experiences sharp drawdowns during sudden VIX spikes (equity market selloffs), as VXX spikes more violently than VXZ in the short term.
+
+## Key Parameters / Signals
+- Contango in VIX futures curve: the necessary condition for the strategy to profit
+- h = ρ · σ_X / σ_Z: hedge ratio (number of VXZ units per 1 unit of VXX shorted)
+- Roll loss differential between VXX and VXZ: the carry being harvested
+- VIX level and slope of futures curve: risk indicators
+
+## Variations
+
+### 7.3.1 Hedging Short VXX with VIX Futures
+Instead of using VXZ to hedge, use a basket of N medium-maturity VIX futures (e.g., months 4-7) directly. The optimal weights w_i for the N futures:
+
+```
+w_i = σ_X Σ_{j=1}^N C_{ij}^{-1} σ_j ρ_j                           (432)
+```
+
+where:
+- ρ_j: historical correlation between futures j and VXX returns
+- C_{ij}: N×N sample covariance matrix of the N futures returns (C_{ii} = σ_i²)
+- σ_X: historical volatility of VXX
+
+Dollar-neutral constraint (optional): Σ_i w_i = 1  (Eq. 433). Some w_i may be negative; can impose w_i ≥ 0 if short futures is undesirable.
+
+Portfolio can be rebalanced monthly or more frequently. This variation allows finer control over the hedge than using VXZ alone.
+
+## Notes
+- VXX spikes (which occur during equity market selloffs) can be large and sudden, causing substantial short-term P&L drawdowns even if the strategy is profitable overall.
+- The hedge ratio h should be recalibrated periodically using updated historical data.
+- The corresponding VXZ spikes are typically smaller, providing only partial protection during stress.
+- Transaction costs (bid-ask spread on VXX/VXZ) and ETN management fees must be accounted for in return estimates.
+- In sustained backwardation periods, both VXX and VXZ can rise; the strategy may lose money if VXX rises faster than VXZ.