Value opencode Go plan requests; per-duration cache prices; usage under answers

- opencode Go reports plan requests as cost 0 with the usage in allowance;
  ModelConfig::cost values them at the model's list prices (charged amounts
  and free requests stay as reported). Rows booked at 0 are valued once on
  start (idempotent).
- opencode's price list now has per-duration cache prices for some models
  ({"30m": ..., "12h": ...}): the shortest duration is used, also in tiers.
  Saving the provider's models failed with "untagged enum ModelEntry".
- Each answer shows tokens sent/received and the cost of the turn's requests
  (usage.cost filled when messages are saved and loaded).
- The chat title keeps a minimum width in a crowded top bar.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/store.rs

@@ -653,6 +653,39 @@ impl Store {
         Ok(json!({"total": total, "by_model": by_model, "by_agent": by_agent, "first": first, "last": last}))
     }
 
+    /// Plan requests booked at 0 (opencode Go reports nothing charged, only `allowance`):
+    /// (row id, ts, "provider/model", usage).
+    pub fn plan_requests_without_cost(&self) -> Result<Vec<(i64, i64, String, crate::types::Usage)>> {
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn.prepare(
+            "SELECT id, ts, provider || '/' || model, input_tokens, output_tokens, cache_read_tokens, cache_write_tokens, allowance
+             FROM usage WHERE cost = 0 AND allowance > 0",
+        )?;
+        let rows = stmt
+            .query_map([], |r| {
+                Ok((
+                    r.get(0)?,
+                    r.get(1)?,
+                    r.get(2)?,
+                    crate::types::Usage {
+                        input_tokens: r.get::<_, i64>(3)? as u64,
+                        output_tokens: r.get::<_, i64>(4)? as u64,
+                        cache_read_tokens: r.get::<_, i64>(5)? as u64,
+                        cache_write_tokens: r.get::<_, i64>(6)? as u64,
+                        allowance: r.get(7)?,
+                        ..Default::default()
+                    },
+                ))
+            })?
+            .collect::<rusqlite::Result<Vec<_>>>()?;
+        Ok(rows)
+    }
+
+    pub fn set_usage_cost(&self, row: i64, cost: f64) -> Result<()> {
+        self.conn.lock().unwrap().execute("UPDATE usage SET cost = ?2 WHERE id = ?1", params![row, cost])?;
+        Ok(())
+    }
+
     /// Global statistics in [from, to) (ms). `tz_offset_min` shifts day/hour buckets
     /// into the viewer's local time.
     pub fn global_stats(&self, from: i64, to: i64, tz_offset_min: i64, user: Option<&str>) -> Result<Value> {