test: 100% coverage for mfi + psar + cmf + hma + obv (#27)

* test(mfi): cover period accessor, name, flat-TP fallback

Codecov flagged 8 lines in indicators/mfi.rs (file at 93.10%): const
accessor period (58-60), (0.0, 0.0) arm when tp==prev (85), the
Some(50.0) flat-flow fallback (105), and Indicator-impl name body
(132-134). Add accessors_and_metadata and flat_typical_prices_default_to_50.
mfi.rs now at 116/116.

* test(psar): cover warmup/name, drop cold format-arg + panic-only asserts

Codecov flagged 8 lines in indicators/psar.rs (file at 95.69%):
warmup_period (206-208), name (220-222), the cold format-arg line
254 in pure_uptrend_sar_below_lows, and the in-loop assert! at line
275 in pure_downtrend_sar_above_highs (its panic body is dead).

Add accessors_and_metadata for warmup/name. Refactor both trend
tests to collect violations into a Vec and assert once outside the
loop — the single assert can now legitimately reach its panic body
in a regression, while removing the dead cold-path lines from the
happy-path coverage.

* test(cmf): cover period accessor, name, zero-range branch

Codecov flagged 7 lines in indicators/cmf.rs (file at 95.03%): const
accessor period (71-73), the range==0.0 zero-MFV branch (84), and
Indicator-impl name body (124-126). Add accessors_and_metadata and
zero_range_candle_contributes_zero_mfv (flat H=L=close candles).
cmf.rs now at 141/141.

* test(hma): cover period accessor + name, kill dead naive panic arm

Codecov flagged 7 lines in indicators/hma.rs (file at 92.22%): const
accessor period (51-53), Indicator-impl name body (87-89), and the
unreachable  arm at line 167 in matches_independent_wmas.
Refactor that test to assert the warmup-shape invariant via
assert_eq!(got.is_some(), want.is_some()) + if let, removing the
dead panic arm. Add accessors_and_metadata covering period/name.
hma.rs now at 90/90.

* test(obv): cover value() Some branch + warmup/name metadata

Codecov flagged 7 lines in indicators/obv.rs (file at 92.92%): the
Some(self.total) branch of value() (47) — only the None branch was
hit by reset_clears_state — plus Indicator-impl warmup_period
(79-81), name (87-89). Add accessors_and_metadata covering all four.
obv.rs now at 99/99.

crates/wickra-core/src/indicators/cmf.rs

@@ -214,6 +214,34 @@ mod tests {
         assert!(matches!(ChaikinMoneyFlow::new(0), Err(Error::PeriodZero)));
     }
 
+    /// Cover the const accessor `period` (71-73) and the Indicator-impl
+    /// `name` body (124-126). `warmup_period` is covered elsewhere.
+    #[test]
+    fn accessors_and_metadata() {
+        let cmf = ChaikinMoneyFlow::new(20).unwrap();
+        assert_eq!(cmf.period(), 20);
+        assert_eq!(cmf.name(), "CMF");
+    }
+
+    /// Cover the `range == 0.0` defensive branch (line 84). All other
+    /// tests use H != L candles; feed all-flat candles (H == L) so the
+    /// MFV computation must take the zero-range fallback and emit MFV = 0.
+    #[test]
+    fn zero_range_candle_contributes_zero_mfv() {
+        let mut cmf = ChaikinMoneyFlow::new(3).unwrap();
+        let candles: Vec<Candle> = (0..5)
+            .map(|i| Candle::new(10.0, 10.0, 10.0, 10.0, 5.0, i).unwrap())
+            .collect();
+        let last = cmf
+            .batch(&candles)
+            .into_iter()
+            .flatten()
+            .last()
+            .expect("emits");
+        // Every bar contributed 0 to mfv_sum, so the ratio is 0.
+        assert_eq!(last, 0.0);
+    }
+
     #[test]
     fn reset_clears_state() {
         let candles: Vec<Candle> = (0..20)