feat: flag quotes behind the latest IDX session (#50)

MSN can serve the previous session's close for hours after IDX closes;
on 2026-10-16 at 16:53 WIB it still returned the 15th. Quotes and
screener rows now carry `behind_session`, true when `as_of` is before
the latest weekday whose session has ended (16:15 WIB). It is computed
on return, not cached. The quote table notes such quotes, and the
get_quotes description explains the field.

Closes #50

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V3syn2fN2LNo5pvTSqc6eh

crates/idx-core/src/api/msn/map.rs

@@ -70,6 +70,7 @@ pub(super) fn parse_quote(symbol: &str, quotes: &[MsnQuote]) -> Result<Quote, Id
         prev_close,
         avg_volume: round_u64(quote.average_volume),
         as_of: crate::api::parse_as_of(quote.time_last_traded.as_deref()),
+        behind_session: false,
     })
 }
 
@@ -718,6 +719,7 @@ pub(super) fn parse_screener_results(raw: &RawScreenerResponse) -> Result<Vec<Qu
                 prev_close,
                 avg_volume: round_u64(q.average_volume),
                 as_of: crate::api::parse_as_of(q.time_last_traded.as_deref()),
+                behind_session: false,
             })
         })
         .collect();

crates/idx-core/src/api/types.rs

@@ -50,6 +50,12 @@ pub struct Quote {
     /// Suspended stocks can carry a last trade months in the past.
     #[serde(default)]
     pub as_of: Option<DateTime<FixedOffset>>,
+    /// True when `as_of` is before the latest IDX session that has ended: the
+    /// provider has not caught up yet (MSN can lag hours after the close), or
+    /// the stock did not trade. False when `as_of` is unknown. Set when the
+    /// quote is returned, not when it is cached.
+    #[serde(default)]
+    pub behind_session: bool,
 }
 
 /// OHLC candle data normalized from Yahoo Finance chart indicators.

crates/idx-core/src/api/yahoo/map.rs

@@ -64,6 +64,7 @@ pub(super) fn parse_quote(symbol: &str, chart: &ChartResponse) -> Result<Quote,
             .regular_market_time
             .and_then(|ts| chrono::DateTime::from_timestamp(ts, 0))
             .map(|t| t.with_timezone(&crate::api::idx_offset())),
+        behind_session: false,
     })
 }