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/hma.rs

@@ -128,6 +128,16 @@ mod tests {
         assert!(Hma::new(0).is_err());
     }
 
+    /// Cover the const accessor `period` (51-53) and the Indicator-impl
+    /// `name` body (87-89). `warmup_period` is covered by
+    /// `first_emission_matches_warmup_period`.
+    #[test]
+    fn accessors_and_metadata() {
+        let hma = Hma::new(9).unwrap();
+        assert_eq!(hma.period(), 9);
+        assert_eq!(hma.name(), "HMA");
+    }
+
     #[test]
     fn first_emission_matches_warmup_period() {
         let prices: Vec<f64> = (1..=40).map(f64::from).collect();
@@ -155,16 +165,16 @@ mod tests {
         let mut half = Wma::new(4).unwrap(); // (9 / 2).max(1)
         let mut full = Wma::new(9).unwrap();
         let mut smooth = Wma::new(3).unwrap(); // round(sqrt(9))
-        for &p in &prices {
+        for (i, &p) in prices.iter().enumerate() {
             let got = hma.update(p);
             let want = match (half.update(p), full.update(p)) {
                 (Some(h), Some(f)) => smooth.update(2.0 * h - f),
                 _ => None,
             };
-            match (got, want) {
-                (None, None) => {}
-                (Some(a), Some(b)) => assert_relative_eq!(a, b, epsilon = 1e-9),
-                _ => panic!("HMA and the independent-WMA reference disagree on readiness"),
+            // HMA and the independent WMA chain share a warmup formula.
+            assert_eq!(got.is_some(), want.is_some(), "readiness mismatch at {i}");
+            if let (Some(a), Some(b)) = (got, want) {
+                assert_relative_eq!(a, b, epsilon = 1e-9);
             }
         }
     }