feat: order-book microstructure indicators (part 1 of 4) (#112)

* feat(core): add microstructure input types (OrderBook, Trade, TradeQuote)

New non-OHLCV value types for the order-book / trade-flow indicator family:
Level, OrderBook (sorted, uncrossed depth snapshot), Side, Trade (with
aggressor side), and TradeQuote (trade paired with prevailing mid). Each has a
validating constructor plus a new_unchecked hot-path constructor, with full
unit coverage. Adds InvalidOrderBook / InvalidTrade error variants.

* feat(core): add 5 order-book microstructure indicators

OrderBookImbalanceTop1/TopN/Full (signed depth imbalance), Microprice
(size-weighted fair value), and QuotedSpread (top-of-book spread in bps). All
consume the OrderBook snapshot type, emit f64, are stateless and ready after
the first snapshot, with full unit coverage. Registers a new Microstructure
family in the taxonomy.

* feat(bindings): expose order-book microstructure indicators

Python, Node, and WASM bindings for OrderBookImbalanceTop1/TopN/Full,
Microprice and QuotedSpread. Each takes a depth snapshot via four equal-length
(bid_px, bid_sz, ask_px, ask_sz) arrays. Python and Node expose a batch over a
list of snapshots; WASM exposes per-snapshot update (the streaming model that
fits a browser book feed). Regenerates node index.d.ts/.js and registers the
new InvalidOrderBook/InvalidTrade arms in the Python error mapping.

* test(bindings,fuzz): cover order-book microstructure indicators

Python: smoke, reference values, streaming-vs-batch, lifecycle/repr and input
validation (mismatched lengths, crossed book, misordered levels, zero levels)
for all five order-book indicators. Node: reference values, streaming-vs-batch,
and rejection cases. Adds an indicator_update_orderbook fuzz target driving
every order-book indicator over arbitrary (incl. degenerate) snapshots.

* bench(microstructure): synthetic order-book benchmarks

Add a bench_orderbook_input harness and synthesise a five-level book around
each candle close (no order-book dataset ships with the repo). Benches the
cheapest (top-of-book imbalance) and most-expensive (full-depth imbalance) plus
microprice, matching the curated cheapest/expensive-per-family approach.

* docs: add Microstructure family + bump indicator counter to 224

README gains the Microstructure family row (order-book imbalance, microprice,
quoted spread) and the indicator counter goes 219 -> 224 across seventeen
families; CHANGELOG records the new order-book indicators and value types.

bindings/python/tests/test_input_validation.py

@@ -166,3 +166,28 @@ def test_family_10_ehlers_rejects_invalid_parameters():
         ta.MAMA(0.05, 0.5)
     with pytest.raises(ValueError):
         ta.EmpiricalModeDecomposition(20, 0.0)
+
+
+def test_orderbook_topn_zero_levels_raises():
+    with pytest.raises(ValueError):
+        ta.OrderBookImbalanceTopN(0)
+
+
+def test_orderbook_unequal_price_size_lengths_raise():
+    # bid_px has 2 entries but bid_sz has 1 -> mismatched -> ValueError.
+    with pytest.raises(ValueError):
+        ta.OrderBookImbalanceTop1().update([100.0, 99.0], [1.0], [101.0], [1.0])
+    with pytest.raises(ValueError):
+        ta.Microprice().update([100.0], [1.0], [101.0, 102.0], [1.0])
+
+
+def test_orderbook_crossed_book_raises():
+    # best_bid (102) >= best_ask (101) is a crossed book -> rejected.
+    with pytest.raises(ValueError):
+        ta.QuotedSpread().update([102.0], [1.0], [101.0], [1.0])
+
+
+def test_orderbook_misordered_levels_raise():
+    # Bids must be strictly descending in price.
+    with pytest.raises(ValueError):
+        ta.OrderBookImbalanceFull().update([99.0, 100.0], [1.0, 1.0], [101.0], [1.0])