feat: add occurrence-aware appointment search

docs/PRODUCT.md

@@ -70,6 +70,8 @@ The full terminal is treated as a responsive canvas:
 | Move between editor fields | `Tab` / `Shift-Tab`, arrows |
 | Save/cancel editor | `Ctrl-S` / `Esc` |
 | Return to month/unfocus | `Esc` |
+| Search appointments | `/`, then type and press `Enter` |
+| Choose search result | arrows, `j` / `k`, then `Enter` |
 | Help | `?` |
 | Quit | `q` |
 
@@ -81,8 +83,10 @@ read-only instead of being discarded. Saves reject external changes, retain a
 last-known-good backup, and feed bounded session undo/redo history. Supported
 recurring instances appear throughout the month, preserve civil time across
 daylight-saving changes, and expose their source zone and whole-series mutation
-semantics in the reader. The next local-data work adds `/` search, agenda and
-calendar visibility views, then advanced recurrence overrides and rule editing.
+semantics in the reader. `/` searches occurrence-aware title, description,
+location, and calendar-ID matches in a finite ten-year window centered on the
+selected date. The next local-data work adds agenda and calendar visibility
+views, then advanced recurrence overrides and rule editing.
 
 ## Accessibility