refactor(tours): the map stage's track pick and the planner's focus points in hooks of their own

The tour map stage and the trip planner page hook had grown past the
complexity and length the lint ratchet holds them to. Marking a spot on a
recorded paddle track moves into useTrackLinePick, and what the planner map
frames into usePlannerFocusPoints, each with its own tests. The planner's
viewport snapshot no longer reads a ref while rendering, so the count of
that warning goes down by one.

client/scripts/eslint-baseline.json

@@ -8,7 +8,7 @@
     "trek/no-swallowed-catch": 133,
     "max-params": 35,
     "trek/store-without-selector": 69,
-    "react-hooks/refs": 560,
+    "react-hooks/refs": 559,
     "react-hooks/set-state-in-effect": 197,
     "@typescript-eslint/no-floating-promises": 167,
     "react-hooks/exhaustive-deps": 121,