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/obv.rs

@@ -99,6 +99,21 @@ mod tests {
         Candle::new(close, close, close, close, volume, 0).unwrap()
     }
 
+    /// Cover the `value()` Some branch (line 47) and the Indicator-impl
+    /// `warmup_period` (79-81) + `name` (87-89). `reset_clears_state`
+    /// hits only the None branch of `value()`; the metadata methods were
+    /// never queried.
+    #[test]
+    fn accessors_and_metadata() {
+        let mut obv = Obv::new();
+        assert_eq!(obv.warmup_period(), 1);
+        assert_eq!(obv.name(), "OBV");
+        assert_eq!(obv.value(), None);
+        obv.update(c(10.0, 100.0));
+        // Baseline 0 — value() Some branch.
+        assert_eq!(obv.value(), Some(0.0));
+    }
+
     #[test]
     fn first_candle_baseline_zero() {
         let mut obv = Obv::new();